This offseason, the NFL approved a new rule change to low blocks that limit their use to a box that’s two yards outside of the tackle and five yards on either side of the line of scrimmage from which they can be initiated. Low blocks are illegal by any player everywhere else on the field during a scrimmage down.
Inside the box, blocks below the waist may be initiated except on blocks already illegal, such as crackback blocks.
Here’s the new low block rule, which expands the prohibition against blocking below the waist.