as ), but also must have great hand and foot coordination to successfully protect against pass rushes. If a team has a right-handed quarterback, the left tackle is usually the best pass blocker on the line since they are responsible for preventing a "blindside" pass rush the quarterback might not see. Right tackles have the same responsibilities with left-handed quarterbacks. Backs Backs are so named because they line up behind (in back of) the line of scrimmage at the start of the play. Quarterback: The Quarterback ("QB") lines up directly behind the center, where they take the ball (in an action called the 'snap') and puts it into play. The quarterback's primary duty is either passing (throwing) the ball or handing the ball to a running back ("RB") who carries the ball downfield. In some cases the quarterback is called upon to run the ball downfield themself, either because the play is designed that way or the quarterback has no other options available. A quarterback can even act as a receiver, catching a pass thrown by another player during a "trick play". In most cases, the quarterback also communicates to the other players the play they are going to run correctly, both in the huddle before the team lines up to execute the play and immediately before the ball snap. Quarterbacks must be quick to 1.read defenses accurately and 2.precisely throw the ball. As the leader of the offense, the Quarterback is considered by many to be the most important player on the offensive field. Fullback: The Fullback ("FB") lines up behind the quarterback and is involved in running, blocking, and (in some cases) catching passes. In many offensive schemes the fullback is considered to be a running back, but this player is usually bigger and more physical than other running backs on the team and is more involved in blocking than in running or receiving. Halfback: The Halfback ("HB"), also referred to as a "tailback" ("TB") or more generically as a running back, lines up behind the quarterback and in many cases behind the fullback, or rarely behind center to receive the snap (see Wildcat formation). A halfback's responsibilities include running the ball, catching passes, blocking, and sometimes even throwing the ball on trick plays. Receivers (Eligible receivers are the ends and the backs, other than an NFL quarterback lined up "under center". Not all backs fall into the