A caster is a single, double, or compound wheel mounted to the bottom of a larger object to make the object movable with little or less effort. Casters can be swivel wheels or rigid casters. They are available in various sizes, and are commonly made of rubber, plastic, nylon, aluminum, or stainless steel.
Casters can be seen in everyday applications including shopping carts, office chairs, platform trucks, utilities carts, and dollies. Due to their relatively small wheel size, casters operate well on smooth and flat surfaces but not suitable for carpets, rough or bumpy surfaces.