*In this feature, Football 101, NFL officials help explain and clarify some of the rules that impact the game. This week, back judge Tony Michalek explains when offensive players can and can't use the crown of their helmet:
Summary From The Official NFL Rule Book - Rule 12, Section 2, Article 8
It is a foul if a runner or tackler initiates forcible contact by delivering a blow with the top/crown of his helmet against an opponent when both players are clearly outside the tackle box (an area extending from tackle to tackle and from three yards beyond the line of scrimmage to the offensive team's end line).
Incidental contact by the helmet of a runner or tackler against an opponent shall not be a foul.
The Official Point of View
"[A player is] allowed to, inside the box," Michalek explained. "If he gets outside the box and he squares up - now, squares up is a really important part of it.
"As soon as gets out and he squares up to a defender and tries to bowl his way through with the crown of his helmet, lines him up, that's the important part."
*Last week, umpire Tony Steratore and back judge Tony Michalek helped explain what classifies a player as "defenseless." *