One error many people make is thinking a NT (nose tackle) always plays in a 3-4 defense. That is incorrect. It's not about what style of defense is used, but rather about WHERE the tackle lines up. A tackle could be a NT on one play, and then a 3-technique tackle on another play.

In a 4-3 defense, the undertackle (smaller faster guy that shoots the gap/goes after the quarterback) usually plays on the strong side, while the other tackle (the big beefy guy) lines up near the center or guard on the weak side. But if that big beefy guy happens to line up directly in front of the center, then he's called a nose tackle (or a nose guard) for that play.

-LoE


Nose tackle - Wikipedia, the free encyclopedia

Definition
The nose tackle is a defensive alignment position for a defensive lineman in American and Canadian football. The nose tackle aligns across the line of scrimmage from the offense's center before the play begins.

In a traditional 4-3 defensive set, known as a two-gap defensive set, the nose tackle (NT) is one of two defensive tackles, usually on the weak side of the offensive line. His job is to take up the center and weak-side or pulling guard so that the smaller 'rush' end has a 1-on-1 matchup with the offense's blindside tackle. The second defensive tackle sometimes referred to as an 'under tackle', takes up the strongside guard and the strongside end takes up the strongside offensive tackle. A 1-gap scheme relies on an athletic defensive line rather than a large one and does not include a nose tackle. More modern, cover 2 schemes include either four smaller, athletic linemen, like Tony Dungy's scheme, developed in Tampa Bay; or two small, athletic ends and two nose tackles, like the scheme used by the Baltimore Ravens during their 2000 championship season.

In a 3-4 defensive scheme, the nose tackle is the sole defensive tackle, lining up directly opposite the center in the "0" position. Like the traditional 4-3, the nose tackle must occupy the center and one guard, however in the 3-4 it is typically the strongside guard. One defensive end then matches up with both the strongside tackle and tight end, while the other occupies the weakside guard and tackle. This leaves the outside linebackers free to pass-rush, creating the 3-4 scheme's distinctive pressure on the passing game.



But if you're still intersted, here's more. It's a good article.....
-LoE



FOX Sports on MSN - NFL -

Defensive Line Basics: Mind the Gap

Gaps and Techniques

The "technique" being referred to actually specifies a location on the field and the responsibility that goes with that particular location. If a defensive lineman shifts a few feet to the left or right in relation to the offensive line, his duties (and the skills needed to perform them well) change accordingly.

The various field locations are numbered. These numbers are more-or-less universal: everyone from your local high school coach up to Tony Dungy uses the same numbers:

0-Technique: The defender lines up face-to-face with the center.
1-Technique: The defender lines up on the center's outside shoulder.
2-Technique: The defender lines up on the guard's inside shoulder.
3-Technique: The defender lines up on the guard's outside shoulder, between the guard and the tackle.
4-Technique: The defender lines up on the tackle's inside shoulder, though often coaches want 4-technique linemen face-to-face with an offensive tackle.
5-Technique: The defender lines up on the tackle's outside shoulder.
6-Technique: The defender lines up on the tight end's inside shoulder or (if there is no tight end) about 1.5 yards wide of the tackle.


The numbers break down a little at this point; different coaches will refer to the 7, 8, and 9 techniques in different ways, usually denoting linemen playing anywhere from the tight end's outside shoulder to a yard or two wide of the offensive line. The higher numbers also change depending on whether the player in question is a tackle or end.

Stick a zero on the end of any of these numbers, and they can be used to refer to the locations of linebackers. So a linebacker in 50-technique is off the line of scrimmage, positioned between a tackle and a tight end on the tackle's outside shoulder.

A 3-technique tackle, therefore, is one who usually lines up between the guard and tackle, with all privileges, rights, and responsibilities associated with the position. Each technique comes with a set of reads and keys, specific to the defensive system, the offensive formation, and the down-and-distance situation. In most systems, on most plays, a tackle lined up in 3-technique is supposed to shoot the gap immediately; in a 4-technique, one step to the right or left, his job might be to bottle up the offensive tackle so a linebacker can shoot the gap. In the 2-gap, tackles are often told to "draw responsibility" from two blockers, the football equivalent of "eating space" in basketball.

Why is there so much emphasis on 3-technique tackles lately? Basically, there are two types of tackles. There's the Ted Washington type, who weighs 320 pounds before a meal and is known for his size and power, not his quickness (though many of these players are pretty quick). Then there are players like the Kevin Williams and Rod Coleman: 290-pounders who are quick enough to shoot a gap or execute a stunt. These latter players are 3-technique tackles. The Washington-types aren't called 0-technique or 1-technique tackles because they already have a better name: nose tackles.

The 3-technique tackle is in short supply because few players leave college with the right mix of strength, explosiveness, technique, and durability. Systems like Tony Dungy's rely heavily on 3-technique tackles to disrupt the interior of the offensive line. For most defensive coordinators, heaven is a 3-technique tackle who is in the backfield on every play, a 0-technique tackle who requires two blockers and controls two gaps, and a pass rushing end (7,8,or 9 technique) who also requires a double team on every play.

In addition to the techniques, there are the gaps in the offensive line, which are usually lettered. A-gap is the hole between the center and either guard. The B-gap lies between the guards and tackles. The C-gap lies between the tackles and the tight ends. The D-gap is just off tight end, while coaches will often refer to an E-gap a few yards off the tight end but inside of the wide receivers.



To avoid confusion, coaches use numbered "techniques" to denote pre-snap positioning and lettered "gaps" to tell the defender where his responsibilities lie. So a player in 3-technique with B-gap responsibility will basically be plowing straight ahead at the snap. A 0-technique nose defender with weakside A-gap responsibility will be looping one step to the side of the center where there is no tight end (usually his right).

There's a lot of oversimplification here; coaches will use terms like 2a or 2i technique to represent a player lined up six inches to the tackle side of the guard, for example. A 3-technique tackle doesn't always line up in the 3-technique, just as a tight end doesn't always line up beside the right tackle. Real estate is precious in the trenches, so half a foot can make a big difference.

Colts example: On a typical first down, DT Larry Triplett lines up in 1-technique on the weak side; fellow DT Monte Reagor lines up on the strong side in the 3-technique. DE Raheem Brock is over the tight end in a 6-technique, while Dwight Freeney is in the 7-technique, about 1.5 yards wide of the left tackle on the weak side.

Steelers example: Again on first down, nose tackle Casey Hampton is in the 0-technique, shaded slightly to the weak side. Ends Kimo von Oelhoffen and Aaron Smith are just outside the tackles in 5-technique.

One-Gap vs. Two-Gap

As important as the techniques are, gap responsibilities are much more vital to the success of the defense. Depending on the play called and the philosophy of the defensive coordinator, a defensive lineman could be responsible for either one or two gaps.

One-gap responsibility is relatively simple: the defender attacks a hole and must take care of whatever business happens there. He is expected to tackle any running back who goes through that hole, or to force the running back to move laterally into the arms of another tackler. If the offense is passing, the defender's gap is his route to the quarterback.

Two-gap responsibility requires more discipline on the part of the defender. A defensive tackle may be responsible for both the A and B gaps on his side of the field. His job is not so much to crash through a gap as to read the play, anticipate which gap a running back might choose, and clog it. The two-gap defender must quickly diagnose the blocking scheme to determine which of his gaps is more vulnerable.

No defense uses one-gap or two-gap line schemes exclusively, just as no defense lines up in a two-deep zone on every play. But coordinators have their preferences, and most 4-3 teams use predominantly one-gap schemes, while 3-4 teams will use two-gap responsibilities more often.

Players, for the most part, prefer a one-gap style because it allows them to attack at the snap. Some defenders are far more effective when careening towards a gap than they are while trying to read the offense. In the late 1990's, the Redskins signed DTs Dan Wilkinson and Dana Stubblefield, then used them in a scheme that emphasized two-gap responsibilities. The system negated the strengths of two super-athletic interior players, and the defense suffered as a result. (The coach responsible for the dubious decision: Mike Nolan, under the supervision of Norv Turner.)

Colts example: On the same first down play cited above, all of the defenders have one-gap responsibility except Triplett, who is expected to control both A gaps (the one he is aligned across from and the one on the strong side). Reagor penetrates the B-gap. Brock will loop wide of the tight end and take the D-gap. Though there is no tight end to his side, Freeney will also be considered a D-gap defender because of his wide pass rush: a linebacker will be responsible for the area directly to the left tackle's right side.

Steelers example: Hampton and Smith each have two gap responsibilities: Hampton takes up both A-gaps, while Smith must handle the B and C gaps on the strong side. On the weak side, Kimo will shoot the B-gap, eating up a likely cutback lane, while an outside linebacker worries about the region to Kimo's right.

Rules of Engagement

Controlling a gap isn't a matter of rushing in and waiting for something to happen. At the snap, offensive and defensive linemen begin shuffling and colliding at high speeds. It takes great athleticism, discipline, and alertness for a defensive lineman to do his job.

Ultimately, every lineman wants to defeat his blocker. "Defeating" doesn't mean pile-driving him to the ground and grinning down at him, Mortal Kombat style (though that can sometimes work). To defeat an offensive lineman is to take away his ability to block you. Sometimes, this means driving him backwards so you can steer him like a wheelbarrow. More often, it means out-maneuvering him to a position on the field where he doesn't want you to be. In a two-gap situation, it can mean holding your ground and avoiding the blocker's effort to take you out of a gap.

Coaches stress many fundamental elements when instructing defenders on the basics of defeating an offensive lineman:

"Release quickly and low." First step explosion is key: to beat the blocker out of his stance is to beat him through the whole play. Ineffective linemen stand straight up from their base stance, allowing blockers to get low on them. Coaches focus upon initial footwork techniques to ensure that the defender's knees are bent and his legs are properly spaced.

"Cross the blocker's face." Offensive linemen want to block defenders in a certain direction. By moving across the blocker's face during a slant or loop, a defender forces the blocker to twist his torso and change his blocking angle.

"Get your head past the blocker's hip." Penetrate so quickly that the blocker must turn and engage you parallel to the line of scrimmage. Another common bit of coaching advice: use your blocker as a shield. If you can't reach the gap the running back is headed for, the next best thing is to shove your blocker into it.

"Maintain a vision point." The vision point is often the hip of a guard or tackle, or it can be the V of the neck of the opposing blocker. Watching these body parts helps the defender read the play and the blocking scheme while giving him a location to attack when it's time to smash into the blocker.

"Execute on the offensive side of the ball." If a lineman is executing a stunt, loop, or slant, it's imperative that he does so after penetrating the line of scrimmage; otherwise, the defense is just giving ground.

While we think of defenders as attackers, the opposite can be true in the trenches. Offensive linemen have a variety of ways to make life miserable for the defenders. The cut block is an infamous one, and linemen are drilled in techniques to sweep their legs clear of low blocks. Trap-blocking assignments use the defender's own momentum to lead him right where the offense wants him: far from the ball carrier. And then there is good old-fashioned holding: coaches always stress to defensive linemen the importance of not letting the blocker get his hands and forearms into the lineman's upper body, using punches, rips, and swim moves to keep the jersey from getting grabbed.

Once the blocker is defeated, the defender can make a tackle or a sack. At this point, ball location is critical. Defensive linemen generally don't watch the quarterback at the snap: they read the play by the blocking patterns around them. A lineman peeking at the quarterback won't be tuned in to what his blocker is doing and is likely to get held or cut. Once the defender is in the backfield, he must decide whether he's chasing a running back, attacking a quarterback, dropping off to stop a screen pass, or whatever.

Colts example: Reagor defeats his blocker with quickness, beating the right guard on his first step. The guard's block only slows Reagor a little as he penetrates the backfield. Initial quickness also helps Tripplett, who crosses the center's face, rips with his arms to keep the center from latching on, then holds his position. Brock successfully loops around the tight end, while Freeney's wide rush puts him quickly on the far hip of the left tackle. The Colts have excellent penetration.

Steelers example: Hampton reads the weakside guard: when the guard pulls to the strong side, Hampton reads sweep, so he attacks into the A-gap, where the center does his best to divert him. The tackle on Smith's side takes an initial step to his right (Smith's left) in an effort to hook Smith inside. Smith reads sweep and defeats the block by shuffling left and driving the tackle backwards. On the far side, Kimo easily attacks through the hole vacated by the pulling guard, but the sweep is away from him and he can do little more than pursue the play from behind. Note that with more two-gap responsibilities than the Colts, the Steelers linemen have more decisions to make.

Stunts, Slants, Twists and Loops

A "stunt" is a general term for a play that has defensive linemen attacking gaps other than the ones they are lined up over. Most coaches don't officially call a play a stunt unless two lineman are crisscrossing in some way; this type of play is alternately called a "twist". A "slant" is a diagonal attack by two or more linemen. A "loop" is a variation on the slant, usually executed on the outside of the line.

Stunts have different names in different systems; let's look at one that is often called a "jet." The defensive end and tackle on the weak side of the offense will crisscross on this stunt. The end will take an upfield rush, wide of the offensive tackle, while the defensive tackle drives hard at the guard opposite him. The end then suddenly works back inside against his blocker, who by now is several steps into the backfield. The defensive tackle slips outside of the end and rushes upfield after the end makes his move.

Confused? There's a lot going on there. If the jet stunt works, the offensive guard is rendered irrelevant, the offensive tackle has to play multiple choice, and the pocket collapses. Stunts require precision timing; otherwise, defenders run into each other or blockers calmly switch assignments. Stunts can also leave gaping holes in the line against the running game, so most coaches only call them on the weak side of the formation unless it's 3rd-and-15 (stunts can actually help fill cutback lanes, as blockers have a hard time re-adjusting against stunting defenders when the running back ditches the script).

Slants are more versatile, allowing the defensive line to dictate the flow of a play. A typical slant might have a 5-technique end slanting to the C-gap (essentially crossing the face of the tight end and looping around him), a 1-technique tackle hitting a B-gap (crossing the guard's face), a 3-technique tackle attacking the nearest A-gap, and a backside, 7-technique end shooting the backside C-gap. In other words, everyone is moving to the right, exactly where the offense wants the running back to go. Throw in a blitzing linebacker on the weak side, and the offense is in trouble.

The enemy of the slant is the Alex Gibbs zone-and-cut blocking scheme. Slanting defenders find themselves slanting directly into ambushes as blockers take out their legs or push them along using their own momentum. The enemy of the Alex Gibbs system is the unpopular two-gap philosophy: it's hard to cut block someone who is staying still and waiting for you to try something. So goes the give-and-take of NFL strategy.

Colts Example: On the next set of downs, Dungy replaces Tripplett with the faster Josh Williams and calls a jet stunt to the weak side. Freeney takes his blocker wide, then works inside just as Williams starts to twist wide. Freeney escapes the left tackle but is picked up by a fullback. Williams is too slow to get a sack, but he flushes the quarterback from behind and forces an errant pass. The stunt works, and it gives the opposing line something new to worry about.

Steelers example: The Steelers slant left as part of a blitz package. At the snap, all three linemen (now in one-gap responsibility) slant to the nearest gap to their left: Hampton to strong side A, Kimo to weak side B, Smith looping to strong side D. Linebackers Larry Foote and Joey Porter will blitz on the weak side, Porter from the edge, Foote on a delay into the A gap. The slanting line confuses blitz pickup, and while the fullback engages Porter, Kimo occupies both a guard and tackle, Hampton a center and guard. No blocker peels off to stop Foote when he blitzes a split second later, and Foote records an easy sack.

Wrapping It Up

Defensive line play doesn't occur in a vacuum. Linebackers are involved in many stunts and will sometimes start the play in a three-point stance, lined up in 7-, 8- or 9-technique. When coverage rolls one way, the defensive line often slants the opposite way. And every play is fluid, as a change in blocking schemes or offensive motion can force a sudden change of plans on the D-line.

Hopefully, though, this cleared up a little of the jargon that's thrown around when talking about the defensive line. These lineman aren't 300-pound monsters with no brains; they have to be agile, decisive, alert, focused, and completely versed in the fundamentals of their positions. That's why teams invest so much in their defensive lines: guys with this skill set don't grow on trees.

By the way sapper I was only kidding. LOL but you nickeled and dimed it well.