Glossary of Terms

Automated Storage and Retrieval Systems
A storage rack system / structure where the loading and unloading is typically done by an automated stacker crane or similar operator-less machine.
Applicable Code
The building code that governs the design and installation of a structure. It is typically enforced by local building department officials.
For racks and similar, a “beam” refers to the rigid horizontal structural member.
Beam Locking Device
The mechanism that “locks” the beam connector and column. Typically a pin or bolt.
Braced Frame
This is a vertical truss that provides stability for any rack or structure. They are typically quite strong, and built to resist lateral force.
Cantilever Rack
Commonly used for long material storage (and often used for lumber in your favorite big box home center retailer), a cantilever rack is usually defined by vertical columns with horizontal arms protruding outward, with down-aisle bracing between the columns. The arms can be used for storage or they can support shelves, depending on your needs. Cantilever racks can be both free-standing or tied in overhead.
Case-Flow Rack
This is a specialized “pitched” pallet rack structure where the horizontal shelf beams and/or  case-flow lanes/shelves are supported by the upright frames. It utilizes a pitch, which allows easy loading from one side, and unloading/picking from another.
In plain terms, this is the exterior covering of structure.
Cold-Formed Steel Structural Member
For our purposes, these are racking pieces manufactured from steel plates and/or sheet metal (cold or hot rolled). The forming process is done at room temperature, with the result being a strong, durable product ideal for low to mid-rise applications.
Aka “Transverse Direction”, Cross Aisle is an aisle perpendicular to the storage aisles (think of an aisle running down the middle of a warehouse). It is the opposite of “down aisle”.
Diagonal Bracing
A diagonal component or brace that provides lateral stability. Diagonal bracing will be present in almost any structure.
Storage racks shelves where the loads and/or pallets are stacked one on top of another. A “double stacking” structure will be strong enough to handle this.
Aka: Longitudinal Direction. The is the direction of the principal material handling and storage aisles, and is the opposite of cross-aisle.
Drive-In Rack / Drive-Through Rack
These are vertical upright rack structures that are typically used for “one-wide by multiple-depth” storage. As the name suggests, there is room to drive into (or through) with a pallet jack or forklift. Drive in racks typically include an “anchor section” and are loaded/unloaded from one side, where drive-thru racks do not have the anchor section, and can be accessed from either side.
Used on elevated platforms, pick module walkways, or mezzanines,  guardrails are an essential safety component that protects workers from falling. They usually have two rails (top and intermediate), and multiple posts.


The smooth rail that runs up a stairway for occupants to hold onto as they ascend and descend the stairs.

Aka a “Toeboard”, this is a small vertical plate installed at the edge of an elevated floor, and keeps loose items and debris from falling off the edge.
Movable-Shelf Rack
A storage rack typically used one-deep storage (either hand or pallet). They utilize vertical uprights and horizontal shelving, and are quite adaptable to custom configurations.
Occupancy Category
For our purposes, this is the classification of material handling structures, and is based on their intended use.
Out-Of-Plumb Ratio
Stay with us here: This is the maximum horizontal distance from the centerline of the column at the floor, to a plumb line that extends downward from the centerline of the column at the top shelf elevation. You arrive at the ratio by dividing the previous number by the vertical distance from the floor to the top shelf elevation.
Out-Of-Straight Ratio
This one is a little easier to explain: This is the maximum horizontal distance from the centerline at any point of a column to a plumb line from any other point on the column. This is then divided by the vertical distance between the two points. 
Pallet Beam
The members (both front and back shelf) that bear the weight of any storage load and transfer the load to the upright frames.
Pallet-Flow Rack
A pallet rack where the horizontal shelf beams incorporate pallet-flow lanes (which are usually slightly pitched). This allows for multiple pallet storage, with loading from one side and unloading from the other.
Pallet-Load Support Member
A load-bearing member with its long axis on the horizontal plane. It is used for the support of loads and shelves (and not structural bracing)
Pallet Rack
A common rack and storage structure using vertical uprights and horizontal beams/shelves. Most are built of one and two deep pallet storage.
Pallet Support
An additional support member that’s placed between shelf beams underneath the load.
Pick Modules
A specialized rack structure with interior/central pick aisles. They often utilize one or more platform levels, and have a variety of material handling options (case flow, conveyor, pallet flow, etc.)
For material handling purposes, a Plaque is safety-themed signage depicting the permissible loading of the rack. It is typically a permanent install.
Portable Rack
Aka “Stacking Frames” or “Stacking Rack”, this is typically a four-corner column structure and multiple assemblies, and allows the stacking of goods without applying additional load to the goods on each assembly.
Product Load
The weight of the item(s) placed on the structure / shelf / rack.
Push-Back Rack
This is a specialized pallet rack utilizing tracks and carts to create “push back” storage lanes.  These push-back storage lanes utilize a slight pitch – this allows for loading from the front, where existing items are “pushed back”, and is for “last in, first out” storage.
Rack-Supported Platforms
Exactly what it sounds like – this is a decked / floored work surface that is supported by the rack structure.
Rack-Supported Structure
A heavy-duty rack structure that includes components (usually wall girts and roof purlins) that support wall and roof cladding. The goal is to withstand elements and protect goods from wind, rain, and snow.
Rated Rack Capacity
This is the maximum allowable product load for the designed safety factor, which takes into account load uncertainties; uncertainties in the analysis, material and geometric properties; as well as fabrication and installation tolerances.
Safety Flooring
Flooring in areas where workers may need to venture from the normal pick areas and walkways to manually manipulate and/or dislodge goods.
Seismic Design Category
This is a classification assigned to a structure based on both its occupancy category and the severity of the site’s possible seismic ground motion.
Site Class Definition
This is a classification assigned to a location / building based on the types of soils present.
Structural System
Load carrying components that are assembled to provide either interaction or interdependence.
Trussed-Braced Upright Frame
These are upright frames consisting of two columns, with both diagonal and horizontal bracing attached to/between the columns.
The total weight of the product and the pallet expected to be in a rack.
Upright Frame
A rack assembly that transfers the loads (both vertical and horizontal) to the floor. Typically utilizing two columns with bracing members in-between, the beams of the rack are attached to the columns.
Welded Wire Rack Deck
A rack decking system fabricated from welded wire mesh, and typically reinforced with channels or support wires. This allows additional support for stored material, and also acts as a safety net for unstable loads.

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