There are three basic components of a selective pallet rack.
A) Upright frame: This consists of vertical columns, footplates and horizontal, diagonal and or cross braces. Horizontal shelf beams connect to the upright frames which forms a storage level onto which a palletized load is placed. Generally, two pallets wide is the most common configuration. Three pallets wide is sometimes used for lighter loads. Racking is often arranged in rows of two or more bays, extending in a down aisle direction.
There are many accessories to selective rack examples are listed below:
Decking: Plywood, particle and the most common decking wire mesh panels with channels.
Cross Barmembers or Front to Back Supports: Steel drop in cross bars, double flanged cross bars, 2″ x 4″ wood stringers, 2″ x 6″ wood stringers, the 2″ x 6″ members are the most common.
Other Accessories: Drop on drum supports, drop on skid supports, row spacers, wall ties, overhead top ties, just to mention a few.