Encroachment-When the defense comes across the line of scrimmage and actually touches an offensive player before the snap, encroachment is called. Illegal Shift-A player can not make a motion as if they play were live if they are simply changing their position. Once a player shifts his position he must not make a movement for at least a second before the ball is snapped. More than one player may be shifting at once as long as all get set. Illegal Motion-Similar to illegal shift except the player does not come to a stop. Also, only one player is allowed in motion and the motion must be parallel to the line of scrimmage. Offside-Each team must be lined up on their line of scrimmage and can not be lined up in the neutral zone when the ball is snapped. The neutal zone is the area between the front and back of the ball. False Start-A false start occurs when an offensive player moves before the ball is snapped. This penalty is not called if a player is in motion, but that player must either be moving parallel to the line of scrimmage ( a receiver in motion ) or set before the snap to not be in violation. Motion is a common tool used by coaches to try to free up a receiver, or confuse a defense and is simply a player changing their position on the field before the snap. Only receivers, running backs, and the quarterback may be in motion.