A scrum (short for scrummage) is a method of restarting play in rugby that involves players packing closely together with their heads down and attempting to gain possession of the ball. Depending on whether it is in rugby union or rugby league, the scrum is utilized either after an accidental infringement or when the ball has gone out of play. Scrums occur more often, and are now of greater importance, in union than in league. Starting play from the line of scrimmage in gridiron football is derived from the scrum.