From page 107 of the NCAA rule book: Persons Subject to the Rules Restrictions ARTICLE 2. No person subject to the rules shall commit a personal foul before the game, during the game or between the periods. Any act prohibited hereunder or any other act of unnecessary roughness is a personal foul. a. No person subject to the rules shall strike an opponent with the knee; strike an opponent’s helmet (including the face mask), neck, face or any other part of the body with an extended forearm, elbow, locked hands, palm, fist, or the heel, back or side of the open hand; or gouge an opponent (A.R. 9-1-2-I and II). b. No person subject to the rules shall strike an opponent with his foot or any part of his leg that is below the knee. c. There shall be no tripping (Exception: Against the runner). d. There shall be no clipping (A.R. 9-1-2-III). Exceptions: 1. When offensive players are on the line of scrimmage at the snap within a rectangular area centered on the middle lineman of the offensive formation and extending five yards laterally and three yards longitudinally in each direction, they legally may clip in the rectangular area. http://www.ncaa.org/library/rules/2005/2005_football_rules.pdf