Run Fits

Run fits are based on the defensive philosophy of gap control. Basically each player is responsible for filling a gap (or space between offensive players). A run fit is where the players go post-snap to fill their gap responsibility, it has to be post-snap because all of the gaps move and change after the ball is put into play (think about players getting reached, players pulling and kicking/logging, etc.). On flow to you could be responsible for filling the playside B gap, but on flow away you could be responsible for the playside A gap (think middle LB in 4-3 defense).