A caster (or castor) is an undriven, single, double, or compound wheel mounted on an object to make movement easier. Found on shopping carts, office 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.