[Goldenfleece]

I can cover some of this. The CIAFT can fill in what I miss. Okay, the box is an area extending about 5 yards directly in front of the offensive line. This is the area where defensive lineman and linebackers usually play, so there are normally "7 in the box." However, you can bring the safety up closer to the line, at which point he becomes the eighth man when you talk about "8 in the box." Usually, you bring the safety up for run support or to blitz; however, some teams, like Pittsburgh, will have the safety go into coverage from inside the box sometimes to make the defense harder to read.

Gaps are the holes in the offensive line that a running back could run through. For example, there is a gap between the right tackle and the right guard. So, a gap assignment means a defensive player is responsible to keep the running play from going through a specific gap between two players. The defender assigned to the gap is to keep the hole from opening up enough or tackle the runner coming through if that fails.

A two gap assignment means that the player has to clog two running lanes. The nose tackle in the 3-4 would be assigned to stop the runner from going between (1) the center and left guard or (2) the center and right guard.

I may have some questions for the CIAFT later as well.