Tire swings are a form of swing made from a whole tire. These are often simply a new or used tire hanging from a tree on a rope. On commercially-developed playground swing sets, oversized new tires are often reinforced with a circular metal bar to improve safety and are hung on chains from metal or wooden beams. They may hang vertically or hang flat, suspended from three or more points on one side. The flat version can hold three or more children. Pumping is achieved by using one or two of the three chains attached to the swing, and two (or more) children can pump in turn.