C. There shall be no tripping. Tripping is intentionally using the lower leg or foot to obstruct an opponent below the knee. (Rule 2-28)
Approved Ruling 9-1-2 I. A player on defense sticks out his foot and trips an opponent. (a) The opponent is a wide receiver running a passing route. (b) The opponent is the ball carrier. RULING: (a) and (b) Personal foul, Tripping. Penalty—15 yards, automatic first down.