What is a crackback penalty in football?

Answer 1

NFL Rule 12-2-10

At the snap, an offensive player who is aligned in a position more than two yards laterally outside an offensive tackle, or a player who is in a backfield position at the snap and then moves to a position more than two yards laterally outside a tackle, may not clip an opponent anywhere, nor may he contact an opponent below the waist if the blocker is moving toward the position where the ball was snapped from, and the contact occurs within an area five yards on either side of the line of scrimmage.

Note 1: A player aligned more than two yards laterally outside a tackle at the snap is designated as being flexed.

Note 2: If runner (passer) scrambles on the play, significantly changing the original direction (broken play), the crackback block is legal.

Penalty: Illegal crackback block: Loss of 15 yards.

Answer 2

The term 'crackback' refers to a type of block done by an offensive pass receiver or running back (afterwards referred to as the 'blocker') that is aligned laterally outside of the offensive tackle. The blocker will go in motion, towards the tackle, and when the ball is snapped will run at and make a block on a defensive player that is on or near the line of scrimmage. The block can be very effective if the defensive player is not 'aware of his surroundings' as he will be looking into the offensive backfield and never see the blocker whose responsibility is to take him out of the play.

While the block can be very effective it can also be very devastating. The blocker has a running start and is hitting a defensive player who is usually not expecting to get hit. So there is a rule on the books (NFL) that states if an offensive player makes this type of block, contact with the defensive player must be made at waist height or above if the blocker, in motion towards the offensive tackle, is more than two yards away, laterally, from the offensive tackle at the time of the snap.

One other clause within this rule states that the block is not illegal if made five yards or more down field from the line of scrimmage or five yards or more behind from the line of scrimmage.

If the 'crackback' block is made below the waist and the blocker was two or more yards outside of the tackle at the time of the snap, a 15 yard penalty is assessed for an 'illegal crackback block'.

The gist of the rule is to protect a defensive player's legs as this block is made within a fraction of a second after the ball is snapped.

An example where a crackback block would be used is on a running play that is run wide laterally, such as a sweep. When the ball is snapped, the defensive player (usually a linebacker or defensive end) will see the running back that will take the handoff moving laterally and will do the same only to be met by the blocker in motion.