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.
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 doesn’t, plus whoever the tight end isn’t covering. Usually they defend against defensive ends. In the NFL, offensive tackles often measure over 6 ft 4 in (193 cm) and 300 pounds (136 kilograms).
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.
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.
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; at least one left tackle is almost always picked with one of the first five positions in the NFL Draft. Recent examples include Trent Williams (2010, 4th overall pick), Jake Long (2008, 1st overall pick), and Joe Thomas (2007, 3rd overall pick).
A defensive tackle or DT typically is the largest and strongest of the defensive players. When teams don't have a nose tackle, 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 (also nose 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. The nose tackle aligns across the line of scrimmage from the offense's center before the play begins. In five-lineman 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. The nose guard lines up directly opposite the offensive center, or over the center's "nose". 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 6-18” off the ball. In a reading 50 defense, the nose guards key is to read the offensive center to the ball. In run away, the nose guards job is to shed the blocker and pursue down the line of scrimmage, taking an angle of pursuit. Nose guards tend to be shorter than most other defensive linemen. 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.
thumb|right|A lone nose tackle in the base 3-4 defensive formation In a 3-4 defensive scheme, the nose tackle is the sole defensive tackle, lining up directly opposite the center in the "0-technique" position. Like the traditional 4-3 defensive set, the nose tackle must occupy the center and one guard. Some teams especially in the NFL do have a nose tackle in this scheme. Teams that do have a nose tackle is generally slightly larger and stronger and plays a one technique which means he lines up on either outside shoulder of the center depending on which way the strength of the play is going. The nose tackle's primary job is to stop the run and take on the double team (which is getting blocked by both the center and the weak side or pulling guard) thus freeing up the linebackers to make a play. Some of these examples playing in this scheme are Anthony McFarland who won Super Bowl XXXVII with the Tampa Bay Buccaneers and Super Bowl XLI with the Indianapolis Colts, Gilbert Brown who won Super Bowl XXXI with the Green Bay Packers, and Ted Washington.
However in this 3-4 defense, the nose tackle plays against the center and the weak side or pulling guard. One defensive end then matches up with both the strong side tackle and/or strong side guard, while the other occupies the classic 1-on-1 match up against the weak side tackle. This leaves the outside linebackers free to pass-rush, creating the 3-4 scheme's distinctive pressure on the passing game. In order for a 3-4 to be effective, it needs a dominant nose tackle, which is very hard to find. Ted Washington, who in his prime weighed around 400 pounds, is considered the prototypical 3-4 nose tackle of this era. Because of nose tackles' ability to occupy two offensive linemen, they are more likely to be selected to play in the Pro Bowl, although they are usually selected to fill defensive tackle roster spots. Dominant nose tackles of today include Vince Wilfork, Casey Hampton, Kelly Gregg, Jay Ratliff, Jamal Williams, Kris Jenkins, Antonio Garay, B. J. Raji and Haloti Ngata among others.
- Bryan, Kurt (2009-08-23). ANCHORS are the NEW Position in Football. From the Desk of Kurt Bryan. Retrieved 2009-09-06.
- Weisman, Larry (March 30, 2009), "Keepers of the blind side: Left tackles the new money position", USA Today, http://www.usatoday.com/sports/football/nfl/2009-03-29-sw-tackles-cover_N.htm
- Rush, Nathan (February 8, 2008). "NFL Draft — Defensive Tackles". Athlon Sports. http://www.athlonsports.com/pro-football/12951/nfl-draft-defensive-tackles.
- Dillon, Dennis (2004-10-11). "Getting their nose dirty". The Sporting News. http://tsn.sportingnews.com/exclusives/20041011/572815.html.
|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||Returning||Punt returner, Kick returner|
|Receivers||Wide receiver, Tight end, Slotback||Nickelback, Dimeback||Tackling||Gunner|
|Formations - Nomenclature|