A caster (or castor) is an unriven, single, double, or compound wheel mounted on an object to make movement easier. Found on shopping cart, rolling chairs, and material handling equipment, casters may be fixed to roll in one direction, or mounted on a pivot, such that the wheel will automatically swivel, aligning itself to the direction in which it is moving. Swiveling casters are sometimes themselves attached to handles, so users can turn the caster into the desired direction. Casters are used in many industrial applications. Heavy duty and high capacity casters are used on platform trucks, carts, assemblies, and tow lines in plants.