The 3 technique is right outside the guards either the left or right guard, the 1 technique is right of the center to its left or right. The 3 tech is usually a little lighter and quicker than the 1tech because in the Cowboys system the 1 tech invites the double team., so the 3 tech can be one on one. I have seen it the where the lighter player lines up as a 1 tech and the heavy guy at 3 tech with varied results.