The term used to designate the one-deep shelf type rack. Originally designed for pallets but also used for shelf storage of large units, usually, one or two of a kind. The rack consists of uprights and beams and may be bolted or adjustable. Great care should be exercised in loading racks to avoid overloading. Such racks should be secured to the floor or rows positioned back to back and secured to each other with spacer bars or spacer rods. Beams are usually designed to accept dunnage or cross bracing to prevent loads from falling between the beams.