By far the most common type, consists of end frames (posts), beams, bracing, and frequently decking or support members. Selective pallet rack is the simplest and most economic system for palletized storage where each SKU can be individually stored or retrieved.
The usual arrangement is in a multiple of single and back-to-back rows separated by forklift access (right angle stacking) aisles.
There are a variety of options available to convert a basic frame and beam arrangement to storage of non-palletized loads.