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 league
American football is played on a rectangular field long by 53 1⁄3 yards (48.8 m) wide. Near each end of the field is a "goal line", which are apart. A scoring area called an end zone extends beyond each goal line. Yard lines cross the field every , two rows of hash marks run parallel to the side lines near the middle of the field. At the back of each of the end zones, there are a set of goalposts. American football goalposts were formerly H-shaped and were located on the goal line, but; in 1967, the NFL adopted the current modern offset-fork design, made from extruded steel pipes. The goalposts currently consist of two vertical posts 18.5 feet (5.6 m) apart (24 feet (7.3 m) in high school football) rising from a horizontal crossbar, which is mounted on a single central support post that raises the crossbar to a height of 10 feet (3.0 m), resulting in a two-tined fork shape. The central vertical post is offset from the crossbar toward the rear, placing it as far as possible from the field of play; it is also usually padded to minimize collision-related injuries. In 1974, in the effort to create a safer, unimpeded field of play in the end zone, calculated to produce more passing touchdowns, the NFL relocated the goalposts from the goal line to the end line.