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. They reduce the effort it takes to move the equipment. 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.