An NFL Offense Must Have Seven Players On The Line. Six Is A Five-Yard Penalty.

Some fouls are obvious from the stands. Illegal formation is not one of them - it is a shape requirement, checked at the instant of the snap.

What the rule requires

Rule 7, Section 5, Article 1 says the offensive team must comply with all of the following at the snap: it must have seven or more players on the line, who may lock legs; eligible receivers must be on both ends of the line, and all of the players on the line between them must be ineligible receivers; no player may be out of bounds; and no player may take a position that is neither clearly on, nor clearly off, the line of scrimmage.

The one man who can be in between

There is a single exception to the clearly-on-or-clearly-off requirement: a player directly behind the snapper. Only one player may be in such a position, and he must wear an eligible number unless he has reported in accordance with Rule 5, Section 3, Article 1. Players in eligible positions must likewise wear an eligible number unless they have reported.

Penalty: For illegal formation by the offense: Loss of five yards.

The penalty

• 01Loss of five yards for illegal formation by the offense
• 02It is judged at the snap, so the shape at the snap is what matters
• 03Reporting under Rule 5-3-1 is what legalises an otherwise ineligible number in an eligible spot