What part of a lineman must break the waist of the snapper?

In football, the rule regarding the snapper's position and the formation of the offensive line requires that at the snap, at least a part of one of the lineman's body must break the waist of the snapper. This is essential to distinguish the line of scrimmage and is fundamental for ensuring that the snapper is not unfairly obstructed.

The head or foot of the lineman is the correct response because when a lineman's head or foot is positioned beyond the waist of the snapper during the snap, it fulfills the requirement of being in a legal formation. This positioning directly impacts the ability to execute plays lawfully, ensuring compliance with the rules set forth by the NFHS. Other body parts, such as the shoulders or knees, do not have the same specific requirement in this context, making head or foot the critical elements for determining legality at the line of scrimmage.