Freestanding shelving and shelf racks stand on a floor and provide multiple levels of storage for organizing and staging tools, supplies, and inventory. They make efficient use of vertical space in warehouses, stock rooms, and other storage areas without having to mount shelving to a wall. Metal shelving and shelf racks typically offer more durability than plastic shelving and shelf racks. Wire shelving and shelf racks have openings that allow items to be seen through the shelving, air to pass through the shelving for ventilation, and water to flow through the shelving if fire sprinklers are activated. Plastic shelving and shelf racks weigh less than metal shelving and shelf racks and will not rust. Enclosures install around shelving units to control access to their contents and help prevent theft of high-value items on the shelving units.