The pallet rack is a storage aid system for handling materials designed to store materials on pallets. Although there are many varieties of pallet racking, all types allow the storage of palatalized materials in horizontal rows on various levels. Forklifts are generally required to place loaded pallets on racks for storage. Since World War II, pallet racking has become a ubiquitous item in most warehouses, manufacturing facilities, shopping malls, and other modern warehousing and distribution facilities. All types of pallet racking increase the storage density of stored goods. The costs associated with shelving increase with increasing storage density.