Warehouse Pallet Racking Systems

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AGVS (Automated Guided Vehicle System)

Systems of vehicles that can be programmed to automatically drive to designated points and perform pre-programmed functions. Guidance system may consist of wire embedded in the floor, optical system or other types of guidance. Used frequently in AS/RS distribution centers.

ASRS (Automated Storage and Retrieval System)

 A racking system in which each row has a retrieval unit that picks and puts away items.

Accumulator Conveyor

A conveyor designed to permit accumulation of packages, objects, or carriers. May be roller, live roller, belt, power-and-free, or chain conveyors.


Actual demand created by sales orders or work orders against a specific item.

Automated/Automatic Guided Vehicle

Vehicles equipped with electromagnetic, optical or other systems for guidance and employ various types of collision avoidance systems. AGVs can have reprogramming capabilities for path selection and positioning.  An AGV is often referred to as a driverless vehicle because human intervention is not required to direct the AGV in automatic mode of operation.

Automated Storage/Retrieval System

A combination of equipment and controls, which handles, stores and retrieves materials with precision, accuracy and speed under a defined degree of automation. Systems vary from relatively simple, manually controlled order-picking machines operating in small storage structures, to computer-controlled storage and retrieval systems, totally integrated into the manufacturing and distribution process

Automatic Identification Systems

The application of various technologies, such as bar coding, image recognition, voice recognition and RF/MW transponders, for the purpose of data entry to a data processing system. AIS applications are characterized by data capture at the site of an event. Automatic identification systems combine machine-readable coding symbols to be read by strategically deployed code readers for purpose of automatic sorting, data handling in receiving and shipping, monitoring work in process, and verifying components.

Automatic Sortation

The electronic recognition of cartons by size or code, enabling them to be sorted in groups.

Automatic Warehouse

A warehouse in which a substantial part of the receipt, storage and dispatch functions are performed without manual handling of the goods involved.


The use of computers and other technologies to control industrial machinery and processes


Method for issuing (reducing on-hand quantities) materials to a manufacturing order. With backflushing, the material is issued automatically when production is posted against an operation. The backflushing program will use the quantity completed to calculate through the bill of material, the quantities of the components used and reduce on-hand balances by this amount.


Order for which the merchandise is not available and usually creates a list for re-order and ships when replenished.

Bar Code

A unique identifier comprised of an array of rectangular bars and spaces in a predetermined pattern following specific rules, to represent elements of data that are referred to as characters

Bar Code Reader

A device used to identify and decode a bar code symbol.

Bar Code Scanner

A moving beam used to identify and decode a bar code or other optical symbol.

Batch Manufacturing

The production of parts or material in discrete runs, or batches, interspersed with other production operations or runs of other parts or materials.

Batch Mode Processing

A type of processing in which information from a data collection method is not gathered immediately, but at discrete, non-continuous intervals.

Batch Picking

Order picking method where orders are grouped into small batches. An operator picks one product for a group of orders at the same time; requires sortation and possible consolidation of products for the orders. Typically used when large numbers of orders contain the same SKUs.  An Order Picker will pick all orders within the batch in one pass. Batch picking is usually associated with Pickers with multi-tiered picking carts moving up and down aisles picking batches of usually 4 to 12 orders. However, batch picking is also very common when working with automated material handling equipment, such as carousels.


The part of a conveyor upon which the load or carrying medium rests, rolls or slides while being conveyed.

Belt Conveyor

A continuous fabric, rubber, plastic, leather or metal belt operated over a suitable drive and tail end, and over belt idlers or slider bed for handling materials, packages or objects placed directly upon the belt.

Bi-Directional AGV

An AGV which does not have a dedicated front or back that can automatically operate in the forward or the reverse directions.

Buffer Storage

The part of a warehouse in which back-up or reserve stock is stored, awaiting transfer into active storage.

Bulk Storage

An area in the warehouse set aside for storage of multiple pallets of a given product. Storage in warehouses of any large quantity of supplies, usually in original containers. The area within a facility or warehouse devoted to the placement of large items, floor stocking of pallets and reserve material to re-supply forward picking areas.

Capacity Rated

The rated or design capacity of the material handling equipment as stated by the equipment manufacturer


Automated equipment generally used for picking of small sized, high-volume parts. (Most popular items)

Carousel, Horizontal

Carousels carry a number of storage baskets suspended at the top and bottom by a powered track system. Order picking takes place from the basket which is stopped at an operator station.  Carousels are limited in height to approximately 7 to 10 ft., although greater heights can be obtained by installing additional units on mezzanine levels.   Typical installations for carousel units have multiple carousels that support a single operator station, so that the operator does not have to wait on one machine to index the desired basket position. Can be manually or computer controlled with an integrated inventory control system.

Carousel, Vertical

Similar principal to Horizontal Carousel, but operates vertically with a gimbaled tray suspended between the traction chains.  A manufacturing unit consisting of two or more workstations or machines, with the material transport mechanisms and storage buffers that interconnect them.

Carrying Cost:

The cost associated with having inventory on hand. It is primarily comprised of the costs associated with the inventory investment and storage; also called holding cost.


Describes a unit of measure and the way multiple physical units are packaged.  A case would typically be a sealed corrugated carton, in which a standardized quantity (greater than one) of a specific item is packed.

Chain Conveyor

A conveyor in which one or more chains act as the conveying element. British term: trolley conveyor.


Exterior covering of a structure

Cluster Picking

Product(s) picked to containers by an operator, for multiple orders during a single pass through the pick area. Typically used when the total cube of multiple orders can be manually transported.

Compliance Labels

Standardized label formats used by trading partners. Compliance labels are used as shipping labels, container/pallet labels, carton labels, or piece labels, and usually contain bar codes. Many bar-code labeling software products now have the more common compliance label standards set up as templates.

Computer-Aided Design

The use of an interactive-terminal workstation, usually with graphics capability, to automate the design of products and projects. CAD includes functions such as drafting.

Computer Simulation

The creation of a mathematical model, representing the operation under study, for purposes of testing the implications of possible operating scenarios, without having to implement them.

Consignment Inventory

Inventory that is in the possession of the customer, but is still owned by the supplier. Consignment inventory is used as a marketing tool to make it easier for a customer to stock a specific supplier’s inventory.


From the JIT movement in manufacturing, containerization refers to using standardized containers for the storage and transport of materials within a manufacturing facility, as well as between vendors and manufacturers. The benefits of containerization include reduced product damage, reduced waste (by using reusable containers), less handling, and greater levels of inventory accuracy by simplifying the counting processes.


An electromechanical device or assembly of devices for starting, accelerating, decelerating or stopping a conveyor drive, or that serves to govern in some predetermined manner the electric power delivered to a drive.

Control System

A hardware/software system that has its primary function, the collection and analysis of feedback from a given set of functions for, the purpose of controlling these functions.  Control may be implemented by monitoring and/or systematically modifying parameters or policies used in those functions, or by preparing control reports that initiate useful action with respect to significant deviations and expectations.

Converging Section


A section of roller or wheel conveyor where two conveyors meet and merge into one conveyor


A horizontal, inclined or vertical device used to move or transport bulk materials, packages or objects in a path predetermined by design of the device and having points of loading and discharge fixed / selective; included are vertical reciprocating and inclined reciprocating conveyors.

Conveyor Belt

A belt used to carry materials and transmit the power required to move the load being conveyed.

Conveyor Chain

A chain used to drive the roller in a roller conveyor

Conveyor Guard

A structure mounted below the conveyor path to protect personnel and equipment below from falling material or packages.

Conveyor Width


In unit handling conveyor, the dimensions inside-to-inside of frame rails.  Crab Movement of an AGV in the lateral (sideways) direction, from 0° -90°.


A machine for moving a load vertically and horizontally, with the housing mechanism as an integral part of the machine.

Cross-Belt Sorter

Conveyor sorting system that uses a series of devices (carriers) mounted on a conveyor to sort materials. Each device has a small belt conveyor mounted on top of it that runs perpendicular to the main conveyor. When it arrives at a sort point, the conveyor on the carrier will spin, moving the materials to the side of the main conveyor (usually onto another conveyor, dropping down a chute or into a container).


Cross-docking is the action of unloading materials from an incoming trailer or rail car and immediately loading these materials into outbound trailers or rail cars, thus eliminating the need for warehousing (storage). In reality, pure cross-docking is rare outside of transportation hubs and hub-and-spoke type distribution networks. Many “cross-docking” operations require large staging areas where inbound materials are sorted, consolidated, and stored until the outbound shipment is complete and ready to ship. This staging may take hours, days, or even weeks in which case the “staging area” is essentially a “warehouse”.



The product size: length by width by depth.   The total area inside a truck trailer: the length times the width times the height of the trailer is its cube space.  The true storage capacity of a building: L x W x H.

Cube Utilization

The ratio of space occupied with material to total cubic space available, usually expressed as a percentage.

Cubed Out


A condition where all space in a trailer or container has been completely filled. The term “cubed out” is often used when one has completely filled the trailer or container but is still below the weight capacity. Also see Weighted out. Cycle Count: Process of regularly scheduled inventory counts (usually daily) that “cycle” through your inventory from one item to another

Curved Belt Conveyor

A unit load belt conveyor usually operating horizontally through a 90° or 180° turn.

Cycle Time

Time for a material handling machine to perform one cycle (pick, store, move).  The total time for a process from start to completion.


Distribution center

Decision Point Branches

Intersections or spurs in the guide path or conveyor path

Dedicated Aisles 

An aisle in a warehouse serving only one function (e.g. for order selection, product storage).

Dedicated Storage

A storage policy (usually contrasted with random storage) in which a warehouse location is dedicated to house a specific SKU or SKUs.


The quantity that customers require of a particular item.



An individual technically competent through knowledge, experience, and familiarity with legalities, to design rack storage systems

Dimensional Weight:


The formula used to determine freight charges when the minimum weight-to-volume ratio has not been met. Actual weight and dim weight are compared, and the larger weight is used for the freight calculation. Dim weight was historically calculated as (Length x Width x Height)/194 (in inches). However, recently the carriers have been creating more complex dim weight policies. So depending on the carrier, destination and service, one may be using a different divisor.  The purpose of dimensional weights is to allow the carriers to more effectively apply freight charges when very lightweight but bulky shipments occur which can quickly fill up available space yet not provide enough revenue (based on weight-based fees) to cover costs. Aka: Dim weight Distribution

Discrete Picking 

An operator picks one order, one product at a time. Typically used when order size, distance traveled, and number of total SKUs is small.


The broad range of activities concerned with efficient movements of finished products from the end of the production line or receiving dock, to the consumer; in some cases it may include the movement of raw materials from the source of the supply to the beginning of the production line. These activities include transportation, warehousing, material handling, protective packaging, inventory control, order processing, market and sales forecasting, customer service and attendant management information systems.

Distribution Center

Intermediate warehouse(s) where products from different sources are assembled for shipment and distribution to specific customer locations.


A platform designed to align the floor of a building with the bed of a truck trailer.

Dock Leveler

Device that acts as a bridge between a truck or trailer and the loading ramp. Used for loading vans not flatbeds.

Dock-To-Stock Time 

The elapsed time measured for an inbound item from trailer docking to product put away.


Package filling material. The wood, paper and cardboard wrapping that it takes to secure the items with banding and help protect them (i.e. loose fill packing peanuts, paper, bubble wrap, foam, and air pillows).

Dwell Time

The time equipment spends at a bin front or storage slot waiting for a material handling transaction.


In most cases eaches implies you are using the smallest possible unit of measure (the individual pieces).

EDI - Electronic Data Interchange

The direct communication of data between the computers of two companies or institutions.

The paperless exchange of data including purchase orders and payment information between customer and vendor.

End-Of-Aisle Picking System

High-density mechanized binnable parts systems, such as mini load or carousel units, provides dense storage and maximized use of available storage height. These systems are particularly useful when high transaction rates and large inventory levels result in unacceptably high travel times for man-to-part order picking methods. By delivering the part to the order picker, operator travel time is eliminated. These systems are also effective in situations requiring additional packaging, checking, or processing otherwise impractical on an order-picking industrial truck.

Extendable Conveyor

Used for packaged materials, objects or units. Conveyor types include roller, wheel, or belt. Constructed so the conveyor may be extended or shortened within limits, to suit operational needs.

FIFO (First-In, First-Out)

A method of rotating inventory that allows the oldest products to be used first.  An inventory valuation method, in which costs of materials are transferred in chronological order.  This expression describes the principle of a queue processing technique for product SKU’s.  Products enter the racking from the rear and are removed from the front.  In other words, the first product added to the queue or position in the racking will be the first one to be removed.

Fill Rate

Sales order processing measurement that quantifies the ability to fill orders.

Fixed Beam Bar Code Reader/Scanner

A bar code reader that uses a stationary beam and relies on the relative motion of an item to be read as it passes in front of the reader. Typically called Fixed Bar Code Reader.

Flat Belt Conveyor

A type of belt conveyor in which the carrying run of the conveyor belt is supported by flat belt idlers or by a flat, slider surface.  Portable conveyors that can be expanded, contracted and curved and moveable to wherever needed.

Flexible Manufacturing System (FMS)


An arrangement of machine tools, capable of standalone operation that are interconnected by a work piece transport system and controlled by a central computer. Often consists of an AGV, conveyor or AS/RS delivering work pieces (machine tool pallets) and tools to machines. The transport subsystem, possibly including one or more robots, carries work to the machines, pallets or other interface units so that accurate registration is rapid and automatic. FMS may have a variety of parts being processed simultaneously.

Floor Loading Trucks

A technique used for packing a truck, by hand possibly with conveyors, in which pallets and stretch film are not used.  The load is left on the trailer floor unprotected.

Floor slab

Any floor system, either on or above grade, capable of supporting rack loads.

Flow Analysis

The detailed analysis of the flow of either workers or material, from place (operation) to place. The examination seeks to determine how the progressive travel or the operation may be optimized in terms of both time and material.

Flow Process Chart

A graphic, symbolic representation of the work performed (or to be performed), on a product as it passes through some or all of the stages in a process.

Flue space (pallet rack to pallet rack)

The space maintained between frames using rowspacers or between a frame and a wall using wall spacers. The flue space can also be the distance between pallets and the distance between the pallet and a column.  In sprinkler applications, the column space can be added to form the total flue space.

Food-Grade Warehouse

A Food-grade warehouse is one that meets specific requirements for the storage of edible products or materials that will make up edible products (ingredients or even packaging).


Estimate of future demand needed to be produced to fill orders or inventory

Fulfillment (Fulfill)

The point at which an order is complete; produced, packaged and shipped.

GMA Pallet

Grocery Pallet (or GMA pallet) is built to the specifications of the Grocery Manufacturer’s Association. It is basically a 4-way pallet that is 40 inches wide, by 48 inches deep, by 5 inches high with deck boards and bottom boards mounted flush with the outside stringer.

Gravity Conveyor

Conveyor, usually with wheels or rollers that uses gravity to move items.

Guidance Systems


Guidance systems are used on automated guided vehicles through plants, especially in very-narrow-aisle storage areas. Wire-guided and Rail-guided systems tend to be the most common, but others include laser, optical systems, and magnetic tape.


Path over which an AGV travels. Often such a path contains a guidewire, tape or painted route. Required for communication with the guidance system.

High-Density Storage

Storage in which pallets or cartons are stored more than one unit deep or high. Examples include double-deep selective rack, drive-in, push back, carton flow and pallet flow.


The unused pallet positions in high-density storage that result when the number of unit-loads for an item does not completely fill the storage lane. Since mixing SKUs in high-density storage is normally not done, these unused pallet positions are not available to store other materials.

Intersecting aisle (transverse aisle, header aisle)

An aisle perpendicular to a right angle stacking aisle used by material handling equipment to travel between right angle stacking aisles

I/O (Input/Output)


All activities used to move data in and out of a processor computer.  Also known as Pickup/Deposit station.

Inventory Turn

Number of times inventory is replenished in a specific time period (usually a year as a timeframe); generally calculated by dividing the average inventory level (or current inventory level) into the annual inventory usage.

Inventory Control

A complete inventory management system includes stock levels, stock locations, reorder points, balance-on-hand, item physical description, rotation, etc.

Inventory Turnover Ratio

Measures the return obtained from inventory investments and provides an indication of the movement of materials. Usually expressed as the ratio of annual sales to average inventory investment on hand.

Just-In-Time (JIT)

Term that describes inventory arriving or being produced “just in time” for the shipment or next process; actually a process for optimizing manufacturing processes by eliminating wasted steps, wasted material, and excess warehouse inventory.

LIFO (Last-in-First-out)


The last product entering the storage racking is the first one to be removed (i.e. the newest inventory is used first leaving the older inventory in the rack). This is not an option for food or perishable items, Examples of LIFO are Pushback and Drive-In Rack.

Lead Time

Amount of time required for an item to ship or arrive onsite from the time that it is ordered. This will include purchase order processing time, vendor processing time, in-transit time, receiving, inspection, and packaging times.

License Plate

License plates are often used with warehouse management systems. They are basically an ID number placed on a pallet, tote, carton or other container and are used to track the contents of a container as it moves through the warehouse. The license plate will almost always have a bar code that contains an ID number. By scanning a single bar code on the pallet, complete movement transactions for all items and quantities on that pallet can be tracked.

Lights-Out Warehouse/Facility

A fully-automated facility that requires no human operators and can run with no lights. Requires the use of AS/RS units, AGVs, automated conveyors, and robots.

Loading Dock Platform

An area of a warehouse or other facility where merchandise is received or shipped. The height of the structure is usually designed to conform to the truck bed height on the truck side of a facility, and to rail car bed height at a rail dock.

Local authorities

Building, fire protection, health and safety officials, or any other person designated to represent a regulatory body, that has authority within the jurisdiction based on laws or bylaws passed by a government.

Locator system

Inventory-tracking systems that allows for the assigning of locations of inventory, to facilitate greater tracking and randomly store product. Prior to locator systems, warehouses needed to store product in some logical manner in order for retrieval (e.g. stored in item number sequence, by vendor, by product description, etc.) By using locator systems one can increase space utilization by slotting product via the matching of product physical characteristics product to a location. Productivity can be improved by locating fast moving product to closer, more accessible locations and accuracy increased by separating similar items. Location functionality in software can range from a simple text field attached to an item that notes a single location, to systems that allow multiple locations per item, tracking inventory quantities by location. Warehouse management systems (WMS) take locator systems to the next level by adding functionality, to direct the movement between locations.


The science of planning and carrying out the movement and maintenance of operations. Takes into consideration the design, development, acquisition, storage, movement, distribution, maintenance and disposition of materials.


The characteristic of printed information that permits the direct transfer of information from a printed surface to a data processing system, without operator intervention. Bar coding, optical character recognition and imaging cameras are components of machine reading.


A document that captures information about the freight carrier, class of shipment, shipper, recipient, and other information pertinent to the shipment.

Manufacturing Cell

A collection of machines, grouped together with material handling systems for processing a family of parts or assembly.

Materials Control

The function of maintaining a constant supply of raw materials, purchased parts and supplies needed for production, including requisitioning materials in economic quantities at the proper time (also includes receipts, storage, protection, etc.).

Material Handling


An aspect of materials management relating specifically to the physical transfer of materials.  The movement of materials (e.g. raw materials, scrap, semi-finished and finished) to, through and from productive processes, in warehouses and storage) in receiving and shipping areas.

Material handling equipment

Includes lift trucks and other types of powered equipment used to directly or indirectly load / unload a pallet rack.


A process of bringing together various parts of an order, which have been selected in different picking areas (zones). Also known as consolidation.



A platform supported with structural members, used for storage or operations; constructed at a height that permits movement of people and equipment below.


Inventory system for predicting when an item should be replenished. Once the inventory level reaches a predetermined minimum quantity, a replenishment order (usually automatically) is placed for the difference between.


Describes automated and mechanical transport systems. An elevated conveying system consisting of a rail and load-transporting carrier. The rails typically enclose chain, driven by a motor with mechanisms to engage and transport carriers. Automated Electrified Monorail (AEM) and Electrified Monorail Systems (EMS) provide a supporting rail with continuous electrical feeds. The carriers and off-board controls provide responsive flexibility of pathing and load-handling, including automated loading and unloading.

Non-Value Added Activity

Category or process task that does not add value nor move the product closer to the customer

Occupied Slot

A storage location occupied by a unit load pallet or mini load tote/tray.

Open Order

Order that has not yet been shipped.

Order Allocation

A procedure used when insufficient inventory is available to ship all in-house orders. Management allocates the merchandise through a priority system.

Order Batch

An accumulation of orders released in a batch for order picking.

Order Cycle

The time between orders of a particular item being placed. This can also be called replenishment cycle.

Order Management System


Software that receives customer order information, compares it to inventory availability from the warehouse management system and then groups orders by customer and priority, allocates inventory and determines delivery dates (also called order processing system).

Order Picking

Selection and gathering of items for a customer. Selection of less-than-unit-load quantities of material for individual orders.

Over-And-Under Conveyor

Carriers are mounted and controlled between two endless chains (or other linkage) so that they remain in an upright and horizontal position, throughout the complete cycle of the conveyor.


Pick-To-Light / Put-To-Light

Pallet Inverter

Stationary equipment used to transfer product between different types of pallets such as transferring from wood to plastic pallets, or from pallets to slipsheets. A load on a pallet is placed in the pallet inverter and the entire load is rotated 180 degrees allowing removal of the original pallet and its replacement with another.

Pallet Loader


An automatic or semi-automatic machine consisting of synchronized conveyors and mechanisms to receive objects from a conveyor(s) and place them onto pallets according to a pre-arranged pattern.


The building of a unit load on a pallet to facilitate storing and handling merchandise with a fork truck.


Palletizer is an automatic or semi-automatic machine, consisting of synchronized conveyor(s) and mechanisms to receive cartons from a conveyor(s) and place them onto pallets according to a prearranged pattern. The depalletizer disassembles a pallet load and discharges single cartons.


The assignment of tasks and execution of transactions are conducted electronically without the use of paper documents. This is usually accomplished through the use of fixed or portable computers, bar code scanners, RFID readers, light-signaling technology (pick-to-light) or voice technology.

Pick Aisle

A pick aisle is any aisle in which an order selector can pick orders.

Pick Cart

A manually, or powered, order picking device with wheels, designed to hold small packages and tote boxes.

Pick modules


In a multi-level environment, pick modules are large and complex structures that facilitate the storage and retrieval of loads.  Typically essential to large distribution centres, they are a combination of basic pallet racking components (i.e. uprights and beams) with subcomponents that enable the movement of product with inventory control.  A rack structure comprised primarily of vertical frames and horizontal beams, typically having one or more platform levels of selective, case-flow, or pallet flow bays, feeding into a central pick aisle(s) [work platform(s)] supported by the rack structure.

Pick Time

The amount of time required by an order picker at a pick face, to select material, place it into a picking container and to complete the transaction by marking a picking list or entering “task complete” into a RF terminal or other device. Does not include travel time.


Computer directed picking system using display technology to identify the bin and quantity of a line item to be picked.  Generally applied to carousels, flow rack, and shelving storage systems.  Each pick location is connected to lights and LED displays. Software turns on the light to alert the Order Picker about the location of the next pick and the quantity needed.

Pickup & Delivery (P&D) Station 

A location at which a load entering or leaving storage is supported in a manner suitable for handling by the S/R machine, AGV, AEM or EMS. Also known as pickup & discharge station, transfer station, I/O station or feed/discharge station.


Unit that must be physically picked. See Unit of Issue (U/I).

Pop-up Sorter


Equipment integrated into a conveyor and racking to move products off the conveyor belt at fixed points.

Power-And-Free Conveyor

A conveying system where a load is carried on a trolley or trolleys, mechanically propelled through one part of the system and gravity or manually propelled through another part. Provides a means of switching the free trolleys into and out of adjacent lines. The spur of subsidiary lines may or not be powered. See Monorail.

Positioning Accuracy

The accuracy measured in inches or mm to which an automated vehicle or load on conveyor can stop at a given point (also called stopping accuracy). Measured in horizontal and vertical directions.

Power Conveyor

A conveyor that requires power to move its load. Powered pallet and package conveyor are general classifications, using roller, chain and belt conveying surfaces.


The ratio of output to inputs in pallets or picks, per hour. Amount of work and rate of work attained individually and collectively by the work force.

Pro-Forma Invoice

A sample invoice created to emulate details of the actual invoice for the potential buyer (i.e. a draft invoice). Pro forma invoices are commonly used with international transactions to provide the buyer with the information they will need to pay for the goods (prepayment is common with international transactions) and arrange for import.

Push Sorter:

A fixed-position sorting device used with conveyor systems. A push sorter may use a swinging arm or a simple piston-type pushing device to push materials across the conveyor.


A sorting technique that uses light displays to indicate a container or bin for an order. The operator places line items of the order into the bin matching quantity on display.


A line formed by loads or items while waiting for processing.  Occurs when one or more vehicles or loads, held up behind another vehicle or load, are unable to pass and must wait for the vehicle in front to move on.

Queue Time

The amount of time a job waits at an operation prior to set up or processing; part of manufacturing lead time.

RFID (Radio Frequency Identification)

Systems that use transponders to transmit data to a receiver; often used as part of a real-time locator system where a tag attached to item sends a signal.

RTLS (Real-Time Locator System)

System that uses RFID technology to track the location of tagged objects. Pallets or items have an RFID sensor attached and their location can be tracked anywhere in the distribution center.

Radio Frequency (RF) Transponder

A technology of automatic identification systems that operates on the same principle as security tags placed on clothing. Passive devices are commercially available that will encode and transmit information back to a computer system, when in proximity of the RF transponder.

Radio Frequency (RF) Terminals

Used in conjunction with a Warehouse Management System (WMS) to direct a worker to perform a pick, store or cycle inventory task.  Communicates with the WMS via low power radio frequency transmissions.  Is a real-time link between warehouse tasks and inventory control system.

Random Storage (Floating Slots)

Any SKU may be placed in any unoccupied storage slot of adequate size. Enables strict control of FIFO inventory. Increases storage density above fixed location.

Read Area

Area covered by a scanner. Bar codes must reliably pass through the read area with the length of the symbol parallel to the scan plane.

Reach Truck Area to Divide

Determining optimal aisle width is a critical part of an overall storage/material-handling strategy. Aisle width decisions must attempt to achieve the best combination of productivity, space utilization, flexibility, safety and equipment costs for the specific application.  The primary aisle width constraints include the type of lift trucks used and the characteristics of the loads being handled. Since the load characteristics are difficult to change, the aisle width decision becomes a material handling equipment decision.

Reach Truck

The reach lift truck is designed specifically for racked pallet storage in narrow-aisles (8′-10′ wide). It consists of outriggers in front with telescoping forks that use a hydraulic scissors-type mechanism to pick up / retract the load over the outriggers. This reduces the overall truck and load length, allowing turns in a narrower aisle. Reach trucks are designed for racking areas only and do not work for loading trucks or quickly moving loads over long distances.

Reach Truck – Double Deep

Double-deep reach trucks use an extended reach mechanism that allows storage of pallets two-deep, in specially designed double-deep rack.

Reach Truck – Straddle

Straddle reach trucks are designed to not only slide under pallets, but also grab onto pallet sides, essentially straddling it.

Real Time Processing

The immediate and continuous processing of information gathered from a data collection method.  Communicates continuously with a device while the operation is performed.


The function of accepting, recording and reporting material receipt into a facility.

Receiving Area

Area used for checking, inspecting, and preparing incoming material (both new procurement and returns), prior to delivery to storage areas.


The function of transferring stock from a reserve storage area, or directly from shipping, to a primary picking location which has become empty.

Requirements Planning (DRP)

Process for determining inventory requirements in a multiple plant/warehouse environment.

Resistance factor 


Factor that accounts for unavoidable deviations of the nominal strength from the actual strength and for the manner and consequences of failure.

Reverse Logistics:

Processing of returned items that customers have returned.

RF Devices (Radio Frequency Devices)

Portable data collection devices that use radio frequency to transmit data from scannable tags to the host system.

Right-angle stacking Aisle

The aisle between parallel rows of pallet racks used by material handling equipment, usually lift trucks, to perform right-angle turns for the storing or retrieve of pallets.

SKU (Stock-Keeping Unit)

Used to describe a particular product in one’s stock inventory listing.  One item with a unique identification number specific to that particular part.

SRM (Storage and Retrieval Machine)

A machine operating on mounted rail used for transferring a load from a storage compartment to a P&D station, to a storage compartment. The SRM is capable of moving a load both vertically and parallel with the aisle and laterally placing the load in a storage location. Common types of SRM are mini load and unit load. Usually computer controlled, used for rapid storage and retrieval of merchandise.

Safety Stock

Quantity of an inventory item carried in stores or stock, as a hedge against a stock-out resulting from above-average or unexpected demand during procurement lead-time. Also known as minimum or protective inventory, buffer inventory, cushion or reserve.  Typically the most popular items, or those that take longer to produce, require safety stock for peak customer demand times


The electronic, optical or magnetic search for a symbol that is to be optically recognized.

Shipping Dock

An area reserved for the loading of delivery vehicles.


An inventory adjustment due to pilferage, over or under shipment or receiving errors.


The load-supporting mechanism on the carriage that provides for movement of loads into or out of storage locations and P&D stations

Sizing Station

A station where the profile of loads is automatically checked to ensure they are oriented correctly and are within the proper dimensions for storage.  May incorporate a weigh scale to capture load weight.

Slider Bed

A stationary surface on which slides the carrying portion of a belt conveyor.

Sliding Shoe Sorters


A high speed sortation technology that diverts packages or objects into lanes or chutes. Automatically handles a variety of load lengths


Determining the optimal placement of inventory for picking efficiency.


Generic act (manual or automated) of organizing items into a higher level kit or order.

Sorting Conveyor


A conveyor which receives mixed unit loads or packages and discharges them to segregated spaces or conveyors, in response to an automatic dispatch control. Automatic identification systems are capable of sorting products by shape, color or size.



A path off the main route. A continuous spur is a looped path that rejoins the main path.

Staging Areas

Areas between different warehouse operations where goods are temporarily stored, awaiting processing by the next operation.

Stock Keeping Unit

Represents one unique inventory item (e.g. one style of skirt in six colors and five collar sizes would be 30 different SKUs).

Storage/Retrieval Machine


A machine operating on mounted rail used for transferring a load from a storage compartment to a P&D station, to a storage compartment. The SRM is capable of moving a load both vertically and parallel with the aisle and laterally placing the load in a storage location. Common types of SRM are mini load and unit load. Usually computer controlled, used for rapid storage and retrieval of merchandise.


The spacing boards of a pallet, normally 2” x 4” in size and two to three in number. Top and bottom boards are fastened to the stringers. Coincide with pallet length dimensions.

System Configuration.


An iterative design process consisting of the evaluation of the factors affecting products and production tasks, selection of a design concept based on these factors, and evaluation of the performance of the selected concept. Following the results of the evaluation, a system can be refined and re-evaluated, or discarded

Systems Integrator

A vendor or consultant hired to provide or sub-contract for all equipment/hardware and software needed for an installation.


Any device into which an operator enters or receives information from a computer.

Third-Party Logistics

3PL Businesses provide one or several logistics-related services such as public warehousing, contract warehousing, transportation management, distribution management, freight consolidation.


The amount / rate of merchandise processed through a system or warehouse in a given time, measured in cases, lines or tons of products per hour/day/week. 

Tilt-Tray Sorter

Conveyor system that uses a series of tilting devices to sort items.  A high-speed, continuous-loop sortation conveyor that tilts a tray at a chute, to slide the object into the chutes. Used for consolidating line items of an order.

Travel Time on Platforms

The time for moving material, by industrial truck or person, from one location to another. Often considered in a larger operation, as the total travel time for order fulfillment.

Unit of Issue

The picking quantity (e.g. each, box, bag, etc.)

Unit of Measure

The unit of measure (e.g. weight, length, volume)

Unit Load Weight

The total weight expected to be positioned in the rack, consisting of the product load, container and pallet weight.

Value-Added Activity 

Any change to a product or activity that makes it more valuable to the end customer.

Vehicle Restraint Systems

Devices that prevent trailers from unwantedly moving away from the loading dock. One of the most popular is the ICC bar type restraint system.

Very Narrow Aisle Fork Trucks

Generic category of side-loading fork trucks, using turret and other mechanisms to store and retrieve (pallet) unit loads.

Warehouse Management System 


A computer-based inventory management system for warehouse materials. Uses RF and computer terminals to guide and support receiving, storage, picking, cycle inventory, and shipping operations. Improves inventory accuracy, productivity and customer service.  Manages the storage and movement of items throughout the warehouse and tracks inventory levels and locations.

Wave Picking

An operator picks one order one product at a time for a group of orders.  Picks first in mass and then sorts into individual orders.  Typically used when orders are released to be picked during a specific time period.

Weigh Check Station 

An in line conveyor weigh scale that weighs a passing load and checks that the weight is within acceptable limits. Typically used in a packing and shipping systems’ quality check station to detect shortages and overages.


Material that is in a manufacturing or assembly state between raw material and finished goods.  Goods that are not considered to be a finished product, but must still be accounted for because funds have been invested toward its production.

Work Platform

A work platform increases productivity by raising or lowering a worker to the optimal working height

Zone Batch Picking  

An operator is assigned a zone and picks a part for one or more orders and picks all line for orders stocked in that zone, for more than one order at a time and for multiple scheduling periods during a shift.

Zone Picking:


Method of picking orders in which the warehouse is divided into several zones. Pickers are assigned a specific zone and pick only items in that zone before moving the order (usually via a conveyor system) to the next zone (also called Pick-and-Pass).  Typically used for high speed picking with limited SKUs.