Casters and wheels are used on equipment such as furniture, machinery, or carts to allow the equipment to roll when it needs to be moved or repositioned. Casters each have a wheel that is mounted on an axle and connected to a plate, stem, or other mounting assembly that attaches to the equipment. Wheels have a hole in the center and mount onto the axles or spindles of casters, wheelbarrows, and other material-handling equipment.