Blocking is obstructing an opponent by intentionally contacting him with any part of the blocker’s body.
Pushing is blocking an opponent with open hands.
A block below the waist is a block in which the force of the initial contact is below the waist of an opponent who has one or both feet on the ground. When in question, the contact is below the waist (Rule 9-1-6).
A blocker who makes contact above the waist and then slides below the waist has not blocked below the waist. If the blocker first contacts the opposing player’s hands at the waist or above, it is a legal “above the waist’’ block (Rule 9-1-6).
A chop block is a high-low or low-high combination block by any two players against an opponent (not the ball carrier) anywhere on the field, with or without a delay between blocks; the “low” component is at the opponent’s thigh or below. (A.R. 9-1-10-I-IV). It is not a foul if the blockers’ opponent initiates the contact. (A.R. 9-1-10-V)
Block in the Back
A block in the back is contact against an opponent occurring when the force of the initial contact is from behind and above the waist. When in question, the contact is at or below below the waist (see Clipping, Rule 2-5) (Rule 9-3-6) (A.R. 9-3-3-I-VII and A.R. 10-2-2-XII).
The position of the blocker’s head or feet does not necessarily indicate the point of initial contact.
Frame (of the Body)
The frame of a player’s body is at the shoulders or below other than the back [Rule 9-3-3-a-1-(c) Exception].
The blocking zone is a rectangle centered on the middle lineman of the offensive formation and extending five yards laterally and three yards longitudinally in each direction. (See Appendix C.)
The blocking zone disintegrates when the ball leaves the zone.