Device used to move heavy scenery or equipment in a near frictionless environment. Same principle as arcade Air Hockey, just upside down. When the air supply is removed, the piece rests on the rubber bearings and is immovable. When air is applied, floats
on a cushion of air and is easily movable, albeit in all directions. Disadvantages include having a large, unending supply of compressed air available.
One manufacturer: http://aircasters.com/