<P> The main backfield positions are the quarterback (QB), halfback / tailback (HB / TB) and fullback (FB). The quarterback is the leader of the offense . Either he or a coach calls the plays . Quarterbacks typically inform the rest of the offense of the play in the huddle before the team lines up . The quarterback lines up behind the center to take the snap and then hands the ball off, throws it or runs with it . </P> <P> The primary role of the halfback, also known as the tailback, is to carry the ball on running plays . Halfbacks may also serve as receivers . Fullbacks tend to be larger than halfbacks and function primarily as blockers, but they are sometimes used as runners in short - yardage situations and are seldom used in passing situations . </P> <P> The offensive line (OL) consists of several players whose primary function is to block members of the defensive line from tackling the ball carrier on running plays or sacking the quarterback on passing plays . The leader of the offensive line is the center (C), who is responsible for snapping the ball to the quarterback, blocking, and for making sure that the other linemen do their jobs during the play . On either side of the center are the guards (G), while tackles (T) line up outside the guards . </P> <P> The principal receivers are the wide receivers (WR) and the tight ends (TE). Wide receivers line up on or near the line of scrimmage, split outside the line . The main goal of the wide receiver is to catch passes thrown by the quarterback, but they may also function as decoys or as blockers during running plays . Tight ends line up outside the tackles and function both as receivers and as blockers . </P>

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