Football: What is the Line of Scrimmage?

The line of scrimmage (or the scrimmage line) is an imaginary transverse line that crosses the football field across its narrower dimension, or the line that is parallel to the goal lines. It is where the ball is placed down on the ground before the snap, where the play will begin whether after the most recent play or after the given penalty.
Under the rules of the American Football and the NCAA, there are actually two types of line of scrimmage: the offensive and the defensive. Both lines restrict each side until the ball is at play. The space between the 2 lines is called the neutral zone and no one, except the center, the player in the offensive team who snaps the ball, is allowed to have any part of his body on the neutral zone. For the play to be legal, certain number of players including the eligible receivers must be inches near the line of scrimmage. Although it is technically incorrect, the entire neutral zone is commonly referred to as the line of scrimmage. In order to be specific and avoid confusion, referees, when calling a penalty, often use the term “the previous spot” instead of “line of scrimmage.” Others use the term to refer only to the defensive line of scrimmage since it is the line relevant to the measurements of the progress of the offensive team towards the goal. Under the Canadian Football rules, the players from the defensive team must not go nearer than one yard from the line of scrimmage.
Once the ball is snapped and the play begins, any player from each side is allowed to cross their respective line of scrimmage either to push the ball to the end zone or to stop the ball hander from pushing forward into the field.
On a television broadcast, the line of scrimmage is often indicated with a colored line, usually in blue, through a computer system called 1st & Ten. This is made to help commentators guide their viewers on the progress of the play and for the viewers to clearly see the distance that the ball must travel to get the first down (the yellow line is often used to indicate the distance of the first down from the line of scrimmage). In most broadcast today, the yellow line is changed into red to indicate 4th down.
Tags: football field, football rules, line of scrimmage, scrimmage line