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 football and rugby union
In rugby, the kickoff to begin each half and restarts after scores are taken from the halfway line whereas in American football these can be taken from the 30, 35 or 40 yard line depending on if it is a college, NFL or high-school game. The yard lines of American football are vitally important during game play because a team's advance is measured against them which, in turn, determines possession of the ball. The 22 metre lines in rugby union effectively divide the field into approximate quarters (though not always as rugby pitches vary in size; the total length of the field of play must not exceed 100m but can be shorter than that if space is limited). The 22 metre lines determine the position from which "drop-outs" are taken and also mark the limit where a defending player may kick-the ball directly (without bouncing) into touch without losing the ground gained by the kick.