Running out the clock
In American football, each quarter of a game is measured with a 15-minute game clock, or 12-minute clock in many high school football codes and the German Football League. A team in possession of the lead and the ball will attempt to use up as much of the game clock as possible in order to bring the game to an end more quickly, thus denying the opposition another chance on offense.
Comparison of American and Canadian football
American football rules allow each team to have three timeouts in each half, and the NFL stops play for a "two-minute warning". However, NCAA football has no two-minute warning, but the clock stops on a first down until the ball is ready for play if the play ended in the field of play. In the CFL, each team has two time-outs a game but cannot use both in the last three minutes of the game, while at lower levels of Canadian football each team has two. In Canadian football there is a three-minute rather than a two-minute warning. Also, at all levels of Canadian football, the clock is stopped after every play during the last three minutes of each half. Once the referee has set the ball the clock will restart if the last play ended with a runner tackled in the field of play.