Brian Nix, Head Coach, Alcoa (TN) High School, discusses his version of a tight front defensive alignment. The front call is "Clamp."
The video below is taken from his Vice and Clamp presentation, which you can view in its entirety on Glazier Drive.
In this video, Coach Nix discusses how they teach their Clamp alignment. He shows the pre-snap alignment and techniques with a still frame. Then, he moves to game video--showing both correct execution and some instances where the execution needs improvement.
He likes this formation as it allows the linemen to "waste blockers" for the linebackers to make the tackle.
The inside linebacker's base read is the H Back to the guard to that side. If there is no H Back, they read the tailback to the guard on that side. That changes slightly with the quarterback under center or when facing pistol.
The inside backers know that one of them will become the A gap fitter, the other will become the C Gap fitter. The exact assignments will be determined by the flow of the play.
Their Outside linebackers become the defensive ends. Their reads are "high, low, and flow." Are you getting a high hat from the offensive tackle? A low hat? What is the flow of the play? Is it coming toward you or away from you?