The tackle box in football is an area that is commonly known as the pocket. When a quarterback sets up to pass, particularly at the professional level, he generally does that in the pocket. He will drop back five to seven steps, survey the field and then deliver the ball to a receiver. The quarterback, his blockers and the defensive players must follow several rules when they are in this area.
Tackle Box Definition
The tackle box extends two yards outside the two offensive tackles stationed on the line of scrimmage and goes backward all the way -- in theory -- to the offensive team's goalline. On the standard offensive line, players will line up at left tackle, left guard, center, right guard and right tackle. The starting points of the tackle box are 2 yards to the left of the left tackle's shoulder and 2 yards to the right of the right tackle's shoulder.
When inside the tackle box, the quarterback must attempt to throw the ball directly to a receiver. A quarterback cannot survey the field, determine that none of his receivers are open and then throw the ball away. A quarterback who does that while in the tackle box is guilty of intentionally grounding the football. The penalty for doing that is loss of yardage to the spot where the quarterback threw the ball and loss of down. If the quarterback moves to his right or left, and gets outside of the tackle box, he can throw the ball away by throwing it off the turf or out of bounds, as long as the ball crosses the line of scrimmage.
Offensive linemen who are blocking for the quarterback must be careful not to grab any part of the defensive player they are blocking outside the shoulder pads when they are in the tackle box. Offensive linemen may extend their hands and arms when they block, but they may not grab a handful of uniform while doing so. This is easily noticeable when the offensive lineman is inside the tackle box as the line judge -- one of the game officials -- is charged with watching blocking technique and must make sure it is legal. If not, a holding call is made.
If defensive linemen get through an offensive player's block and have a chance to get to the quarterback and sack him, they have to be quite precise in their tackling technique. For example, the defensive lineman cannot grab the quarterback and slam him to the turf or lead with his helmet. When tackling the quarterback in the tackle box, you must grab the quarterback somewhere above the knees and shoulders and wrap him up while tackling. Leading with the helmet is illegal and so is tackling below the knees. These limitations only apply when hitting the quarterback within the tackle box. If the quarterback has run outside the box or run downfield, the defensive player is allowed to hit or tackle the quarterback as if he were a running back and none of the protective rules apply.