We hear “3-technique tackles” in coach-speak. What does that mean?
It only means where the defender lines up opposite his offensive man.
For instance, a defensive tackle can shift a few feet either way and change from a 4-technique to a 3-technique. That is, he can shift and go down in his stance, just to the outside shoulder of the offensive guard, which is location 3 (hence 3-technique).
If he shifts a little outward and closer to the inside shoulder of the tackle, now he is in the 4 position (hence 4-technique).
It is really that simple.
The image above might be a little complicated. Numbering systems can vary with schemes and shading, so let's refer to the diagram below for simplified “technique” locations. The Os are the O-line and QB:
O O O O O O
6 5 4 3 2 1 0 1 2 3 4 5 6
Here is a list of the techniques for the diagram above:
0-technique: Line up directly in front of the offensive center.
1-technique: Line up on the offensive center’s shoulder (right or left).
2-technique: Line up on the offensive guard’s inside shoulder.
3-technique: Line up on the offensive guard’s outside shoulder.
4-technique: Line up on the offensive tackle’s inside shoulder.
5-technique: Line up on the offensive tackle’s outside shoulder.
6-technique: Line up on the tight end’s inside shoulder (or about a yard or so outside the tackle if no tight end).
Note: You can just add a zero to each number to tell linebackers where to line up. For instance, an outside linebacker might be in a 50-technique, lined up a few yards behind the defensive line naturally and to the offensive tackle’s outside shoulder.
Note: We don’t call a defensive lineman located over or near the offensive center, a 0-technique or a 1-technique defensive tackle. They are usually strong and big (hopefully fast), and they are called “nose tackles.”