Encroachment (gridiron football)

In gridiron football, encroachment refers to when before the snap, a defensive player illegally crosses the line of scrimmage and makes contact with an opponent or has a clear path to the quarterback. In high school, this includes any crossing of the neutral zone by the defense, whether contact is made or not. It is a violation of the game's code. It is similar to offside except when it occurs, the play is not allowed to begin. Like offside violations, the violating team is penalized 5 yards.

The head linesman has the duty of watching out for encroachment and other similar infractions, and the line judge assists in this process.