In American football

American football

American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team's end zone. Known in the United States simply as football, it may also be referred to informally as gridiron football. The ball can be advanced by...

, a trap play, or trap run, is a run consisting of a defender on the line of scrimmage

Scrimmage

A scrimmage, or exhibition game, is an informal sports contest or practice match engaged in for practice purposes which does not go on the regular season record. Scrimmage may also refer to:* Line of scrimmage, in American football and related games...

 (either a defensive tackle or defensive end) getting trap blocked by an offensive lineman or back from the opposite (other side of the center) side of the ball. One of the defensive linemen will remained un-blocked on a trap and either a backside guard/tackle/h-back will pull down the line of scrimmage and kick him out so that the ball carrier can run inside of that trap block.

Typically, flow will start out one way (right or left) and the back will receive the ball going away from flow where the trap is taking place.