Zone Read
Leave the backside DE unblocked and let the QB decide
The Zone Read is the play that revolutionized modern football by merging option principles with zone-blocking schemes. The offensive line blocks inside zone while intentionally leaving the backside defensive end unblocked. The QB meshes with the RB and reads the unblocked DE: if the DE crashes inside to tackle the RB, the QB keeps the ball and runs outside to the vacated edge; if the DE stays home and contains the QB, the QB gives to the RB running inside zone. The beauty is that the offense effectively blocks one more defender than they have blockers for, because the read "blocks" the DE without anyone touching him.
Blocking Assignments
The offensive line executes standard inside zone blocking to the playside — covered linemen block their man, uncovered linemen work combo blocks and climb to linebackers. The critical difference is that the backside tackle does NOT block the backside DE. Instead, the backside tackle zones playside with the rest of the line, leaving the DE as the unblocked "read key." The QB is responsible for that defender via his read: give if the DE stays, keep if the DE crashes. The backside guard may also pull or zone depending on the variant.
Running Back Read
Run standard inside zone — aim for the playside guard's outside hip and read the first covered lineman past center. The RB does not change his run based on the QB's read. Run full speed at the zone-side gap and take the ball if the QB gives it. The QB handles the backside DE read — the RB just runs his inside zone track.
Why It Works
The Zone Read gives the offense an extra blocker for free. By leaving the backside DE unblocked and having the QB read him, the offense effectively "blocks" that defender without using a blocker. This means the other five offensive linemen can all block other defenders, creating a numbers advantage at the point of attack. The DE is wrong no matter what he does — crash and the QB keeps; stay home and the RB has a clean lane. Defenses must resort to exotic solutions like the "scrape exchange" (DE crashes, LB scrapes outside) to defend it.