The defensive tackle is the anchor in the defensive line for a football team. Typically there are two defensive tackles on the field. These two tackles fight play after play in the trenches where they do everything they can to bounce run plays to the outside and to rush the quarterback when it's pass. So where does a defensive tackle line up, and what do they do when the ball is snapped?
The defensive tackle will line up on their assigned man or gap, depending on the defense called. He'll be in either a 3- or 4-point stance, ready to fire off when the ball is snapped.
The defensive tackle is assigned to clog up the gap he's assigned to, or rush through his man to get to the quarterback. The more often he wins his battle in the trenches, the more often the the defense will stop the play.
At The Snap
When the ball is snapped, the defensive tackle is going to fire off the ball as hard as he can, at the same time reading what the offensive lineman is going to do. Whichever way he gets blocked, he will "fight pressure with pressure." In other words, he will fight to go the opposite direction that he feels like that offensive lineman is pushing. He needs to get his hands to the chest, and his eyes in the gap he's assigned to.
If the defensive tackle reads run, he'll fight pressure with pressure to fill his assigned gap and either make the tackle, or cause the play to bounce outside.
If the defensive tackle reads pass, he's got to get separation and get to the quarterback in his pass rush lane. As a general rule, the defensive tackles will push the pocket in from the front, and the defensive ends will collapse the pocket from the outside.
Defensive tackles are two of the most critical positions on the defensive unit. If they can do their job well, they make the other defenders' jobs easier.