In American football, blocking or interference (or running interference) is a legal move occurring when one player obstructs another player's path with his body. The purpose of blocking is to prevent defensive players tackling the ball carrier, or to protect the quarterback while attempting to pass or hand-off the ball. Offensive linemen and fullbacks tend to do the most blocking, although wide receivers are often asked to help block on running plays and halfbacks may be asked to help block on passing plays, while tight ends performs pass block and run block if they are not running routes to receive catches.