Offensive scheme

A formation in American football refers to the position players line up in before the start of a down. There are both offensive and defensive formations and there are many formations in both categories.

At the highest level of play in the NFL and NCAA, the one constant in all formations is the offensive line, consisting of the left and right tackle, left and right guard, and a center. These five positions are often referred to collectively as the "line", and have the primary role of blocking. By rule there must be two additional players on the line of scrimmage called ends. These players are eligible receivers and may play near the linemen (tight ends) or farther away (split end or wide receiver). Most teams play additional players near (but still off) the line of scrimmage to act as extra pass receivers.

Up to four players can be behind the offensive line, but one is always designated the quarterback (defined as the player who receives the ball from the center). Upon the snap of the ball, the quarterback becomes the ball carrier. The ball carrier has five options:

The three other backs can be halfbacks, (who primarily carry the ball), fullbacks, (who primarily block), or they can play near (but not on) the line of scrimmage to act as extra tight ends or wide receivers. A tight end that fills the role as the 4th back is often called an "H-Back" and a wide receiver that fills that role is sometimes known as a "flanker" or a "slot" receiver (depending on where he lines up). Most formations have a "strong" side (the side with the tight end, or the side with more players) and a "weak side" (the side opposite the tight end, or the side with fewer players).

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