also: GDB · gap down backer
The offensive line blocking rule for gap-scheme runs, checking inside gap, down-block, or climbing to a linebacker while leaving head-up defenders for a puller. Primarily used on the playside of Power and Counter, or across the backside on perimeter runs like Jet Sweep.
The core blocking rule for gap-scheme runs like Power, Counter, and Buck Sweep. GDB is primarily executed on the frontside of the play (and across the backside of perimeter sweeps like Jet Sweep), where linemen execute a disciplined inside-out progression:
A defender aligned head up on you is intentionally skipped. In a gap scheme, a head-up defender is not an immediate threat to the interior running lane and is left on the line of scrimmage for a pulling guard's kick-out block. If a lineman mistakenly base-blocks a head-up defender, the puller has nobody to kick out and the linebacker runs unblocked through the vacated gap.
Why backside linemen typically do not follow GDB on interior gap runs: Traditional gap-scheme plays like Power and Counter require backside protection and pullers. If a backside tackle followed GDB on Power, checking inside and climbing to a linebacker would give the backside edge rusher an unobstructed path into the backfield to tackle the runner from behind. Backside linemen on those plays instead execute pull, block-back, scoop, and step-and-hinge assignments. However, on fast perimeter sweeps like Jet Sweep where the ball gets outside immediately, backside linemen use GDB to climb directly to second-level pursuit.
How the unit coordinates on Power (Playside GDB + Backside Protection & Pulling):
The ball carrier presses downhill through the C-gap running lane between the tackle's down block and the pulling guard's kick-out block.
GDB, gap down backergap-on-downGDB is the engine of gap-scheme football because it divorces offensive linemen from static man assignments. By prioritizing inside penetration, down-blocking on adjacent interior linemen, and releasing to second-level linebackers, GDB creates natural double-teams and clean angles against odd or even fronts while leaving edge containment for pullers.