Numbering Exception on 1st, 2nd, or 3rd Down
 

Under what conditions can A have players in the game under the numbering exception on 1st, 2nd, or 3rd down?

Just want to get a clarification if possible.

Thanks

1-2-3 Down- Must be in a scrimmage kick formation and only the snapper may have a number NOT 50-79. He can not be an end and is ineligible.

4th Down- Any numbered A player can take the place of a normally # 50-79 player during a scrimmage kick formation. They too can not be an end and are ineligible