The defensive team is not privy to which type of play will develop. To protect against common plays, their line ends up divided up much the same way as the offense, with the defensive tackle at the front both holding the line as well as attempting to threaten the quarterback, the defensive backs positioned behind the line to protect against pass plays, and the linebackers positioned to counter a rush. Once the play starts, the defensive players tend to collapse towards the action, preventing forward motion of the rush, or blocking a pass. This commitment to a course of action is typically safe; there is only one forward pass allowed per play, so once the ball is passed the rushers are out of the action and all the defenders can attempt to block the receiver, and while anyone can throw the ball forward, doing so is so specialized that once the quarterback hands off the ball or tosses to a runner, the possibility of a forward pass is generally eliminated.