A
rack (sometimes known as a
triangle) is the name given to a frame (usually wood, plastic or metal) used to organize
billiard balls at the beginning of a game. Rack may also be used as a verb to describe the act of setting billiard balls in starting position in
billiards games that make use of racks (usually, but not always, using a physical rack), as well as a noun to describe the balls in that starting position.