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.
Stance (American football)
In the National Football League (NFL), the average amount of plays per game is over 60 per team. This means that, in one game, a lineman playing the entire time could enter a stance more than 60 times. However, it is not likely to be the same stance every time. Furthermore, it is important to remember that the offensive team must remain still for one second prior to the ball being snapped. This means that once an offensive player has become set in a stance, he must stay in it until the ball is snapped and the play begins. Additional motion can result in a false start penalty. Defensive players, on the other hand, are permitted to shift as much as they want before a play. It is possible for a defensive lineman to line up in one stance and then change to another just before the play begins. He can even shift his body to another place.