Diamond racks feature a box joint and doweled corners, outside finger groves, head ball diamond inlay and squaring line on the back side of the rack. If you have a Diamond table this rack can be ordered to match your tables finish. A rack is a metal storage device that is usually made of a durable material. Racks, much like shelves have a wide array of shapes and sizes. Racks are of great use for storage and industrial purposes and are finding their place in the industrial world.