Tackle (American and Canadian football)
Tackle is a playing position in American and Canadian football. Historically, in the one-platoon system a tackle played on both offense and defense. In the modern system of specialized units, offensive tackle and defensive tackle are separate positions.
Offensive tackle 
The offensive tackle (OT, T) is a position of the offensive line, left and right. Like other offensive linemen, their job is to block: to physically keep defenders away from the offensive player who has the football. The term "tackle" is a vestige of an earlier era of football in which the same players played both offense and defense.
A tackle is the strong position on the offensive line. They power their blocks with quick steps and maneuverability. The tackles are mostly in charge of the outside protection. If the tight end goes out for a pass, the tackle must cover everyone that his guard does not, plus whoever the tight end is not covering. Usually they defend against defensive ends. In the NFL, offensive tackles often measure over 6 ft 4 in (193 cm) and 300 lb (140 kg).
According to Sports Illustrated football journalist Paul "Dr. Z" Zimmerman, offensive tackles consistently achieve the highest scores, relative to the other positional groups, on the Wonderlic Test, with an average of 26. The Wonderlic is taken before the draft to assess each player's aptitude for learning and problem solving; a score of 26 is estimated to correspond with an IQ of 112.
Right tackle 
The right tackle (RT) is usually the team's best run blocker. Most running plays are towards the strong side (the side with the tight end) of the offensive line. Consequently the right tackle will face the defending team's best run stoppers. He must be able to gain traction in his blocks so that the running back can find a hole to run through.
Left tackle 
The left tackle (LT) is usually the team's best pass blocker. Of the two tackles, the left tackles will often have better footwork and agility than the right tackle in order to counteract the pass rush of defensive ends. Most quarterbacks are right-handed and in order to throw, they stand with their left shoulders facing down field, closer to the line of scrimmage. Thus, they turn their backs to defenders coming from the left side, creating a vulnerable "blind side" that the left tackle must protect. (Conversely, teams with left-handed quarterbacks tend to have their better pass blockers at right tackle for the same reason.)
A 2006 book by Michael Lewis, The Blind Side: Evolution of a Game, sheds much light on the workings of the left tackle position. The book discusses how the annual salary of left tackles in the NFL skyrocketed in the mid-90's. Premier left tackles are now highly sought after commodities, and are often the second highest paid players on a roster after the quarterback; in the 2013 NFL Draft three of the first four picks were left tackles, and usually at least one left tackle is picked in the first five positions. Recent examples include Eric Fisher (2013, 1st overall pick), Luke Joeckel (2013, 2nd overall pick), Lane Johnson (2013,4th overall pick), Matt Kalil (2012, 4th overall pick), Trent Williams (2010, 4th overall pick), Jake Long (2008, 1st overall pick), and Joe Thomas (2007, 3rd overall pick).
Defensive tackle 
A defensive tackle (abbreviated "DT") is typically the largest and strongest of the defensive players. The defensive tackle typically lines up opposite one of the offensive guards. Depending on a team's individual defensive scheme, a defensive tackle may be called upon to fill several different roles. These roles may include merely holding the point of attack by refusing to be moved, or penetrating a certain gap between offensive linemen to break up a play in the opponent's backfield. If a defensive tackle reads a pass play, his primary responsibility is to pursue the quarterback, or simply knock the pass down at the line if it's within arm's reach. Other responsibilities of the defensive tackle may be to pursue the screen pass or drop into coverage in a zone blitz scheme. In a traditional 4–3 defensive set, there is no nose tackle. Instead there is a left and right defensive tackle. Some teams especially in the NFL do have a nose tackle in this scheme, but most of them do not.
Nose tackle 
Nose tackle (also nose guard or middle guard) is a defensive alignment position for a defensive lineman. In the 3–4 defensive scheme the sole defensive tackle is referred to as the nose tackle. In some 4–3 defensive set, the nose tackle is one of two defensive tackles. Some teams especially in the NFL do have a nose tackle in the 4–3 defensive set, which lines up against the opposing center and very likely the weak-side or pulling guard. The nose tackle aligns across the line of scrimmage from the offense's center before the play begins in the "0-technique" position. In this position, frequently taking on the center and at least one if not both of the guards, the nose tackle is considered to be the most physically demanding position in football. In five-linemen situations, such as a goal-line formation, the nose guard is the innermost lineman, flanked on either side by a defensive tackle or defensive end. According to Pat Kirwan, a traditional 3–4 defense demands "a massive man who can clog up the middle," while a 4–3 defense is looking for "a nose tackle who relies on quickness to penetrate and move along the front."
Typical 3–4 nose tackles are "big wide bodies who can hold the point of attack and force double teams by the guard and center." They are usually the heaviest players on the roster, with weights ranging from 325 to 375 pounds (147 to 170 kg). Also, height is critical, as they are supposed to get "under" the offensive line, which means ideal 3–4 nose tackles are no taller than 6 ft 3 in (1.91 m). Recent examples of such nose tackles include Jamal Williams, Casey Hampton, and Vince Wilfork. Rather uncommon are taller nose tackles, such as Ted Washington and Ma'ake Kemoeatu, both 6 ft 5 in (1.96 m) tall.
In a 4–3 defensive front, nose tackles are rather quick and supposed to "shoot the 'A gap' and beat the center and guard into the backfield." Height is not as important, and their weight is closer to 300 pounds (136 kg).
The terms "nose guard" or "middle guard" were more commonly used with the five-man defensive line of the older 5-2 defense. Effective against the inside run but not the short pass, the 5–2 was phased out of the pro game in the 1950s, but was still used by some major college programs into the 1980s. In the 4-3 defense, the upright middle linebacker replaced the middle guard. The nose guard is also used in a 50 read defense. In this defense there is a nose guard, two defensive tackles, and two outside linebackers who can play on the line of scrimmage or off the line of scrimmage in a two point stance. The nose guard lines up head up on the center about six to eighteen inches off the ball. In a reading 50 defense, the nose guard's key is to read the offensive center to the ball. In run away, the nose guard's job is to shed the blocker and pursue down the line of scrimmage, taking an angle of pursuit. The primary responsibility of the nose tackle in this scheme is to absorb multiple blockers so that other players in the defensive front can attack ball carriers and rush the quarterback.
- Weisman, Larry (March 30, 2009), "Keepers of the blind side: Left tackles the new money position", USA Today
- Rush, Nathan (February 8, 2008). "NFL Draft — Defensive Tackles". Athlon Sports.
- Dillon, Dennis (October 11, 2004). "Getting their nose dirty". The Sporting News.
- "In deep pool of D-line talent, schemes will dictate picks". CBSSports.com. March 6, 2013.
- Dixon, D., (October 18, 2004) http://findarticles.com/p/articles/mi_m1208/is_42_228/ai_n6249316/?tag=content;col1 The Sporting News
|Positions in American football and Canadian football|
|Linemen||Guard, Tackle, Center||Linemen||Tackle, End, Nose tackle||Kicking players||Placekicker, Punter, Kickoff specialist|
|Quarterback||Linebackers||Snapping||Long snapper, Holder|
|Backs||Halfback (Tailback), Fullback, H-back||Backs||Cornerback, Safety, Halfback||Returning||Punt returner, Kick returner|
|Receivers||Wide receiver, Tight end, Slotback||Nickelback, Dimeback||Tackling||Gunner|
|Formations (List) — Nomenclature|