Shelving units are essentially designed to be self-supporting structures. The shelving units are prefabricated structures composed of special rolled steel section, support beams, and shelves; they are reinforced with diagonal bracing. The basic shelving design is one upright frame with shelving bays. The shelving unit frame is made from four uprights of the appropriate height that are interconnected by diagonal on depth from front to back. The shelving frame must always retain two shelves, i.e., two storage levels to ensure the stability of the overall construction. It is also possible to equip the shelving unit with any of the accessories provided.