Defensive tackle is a position that has evolved as much as any at the college level. The type of defensive tackle a program looks for depends on whether it plays primarily a 4-3, which requires two tackles, or a 3-4, which requires one.
More teams play a 4-3 defense. Ideally, one of the defensive tackles is a two-gap-type run stuffer and the other is a quick, inside penetrator. Quickness is very important at this position, and many defensive tackles are very successful pass rushers because they play one-gap techniques and can put inside pressure on the quarterback.
Defensive tackles must be tough enough to mix it up inside and also stack and control the line of scrimmage. Quickness and explosion are the keys here, and one-gap, penetrating-type defensive tackles with some bulk coming out of high school are a sought-after commodity in recruiting.
In the 3-4 defense, the defensive tackle becomes a nose tackle and lines up over the offensive center. The qualities are the same, but he is usually a two-gap-type run stuffer who can occupy two blockers on the inside and free the inside linebackers to make a lot of plays.
A player at the high school level at or above 290 pounds with athleticism and quickness will garner the most attention from college recruiters. Many players may enter college as defensive tackles but will make the transition to the offensive side of the ball and become outstanding offensive lineman.