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.
Running out the clock
In both professional and college football, the offense has 40 seconds (in the Alliance of American Football, 30) from the end of the previous play to run the next play. A team running out the clock will allow the play clock (which records the time remaining until a play must be run) to drain as much as possible before running its next play. In the NFL, this is particularly noteworthy due to the existence of the two-minute warning. If the trailing team has no timeouts remaining and the leading team is in possession of the ball with a first down at the two-minute warning, they can effectively run out the clock and win the game without running another positive play. With two minutes to go (120 seconds), the offense can take three "knees", one each on 1st, 2nd, and 3rd down (using all 40 seconds from the play clock on each), and allow the game clock to expire before having to run a play for fourth down. A similar situation can be had by also achieving a first down inside the two-minute warning. This practice is commonly known as the "Victory Formation", as the offense lines up in a tightly-protective "V" formation to minimize the chances of a fumble or other turnover. (The AAF lets teams run out the clock on three straight victory formations from 90 seconds left in regulation.)