He you go since you didn't know.
http://www.ncaa.org/about/resources/media-center/news/new-rule-protect-passers-low-hits
The NCAA Playing Rules Oversight Panel, which met via conference call Wednesday, approved a new football rule to better protect passers from contact at or below the knee
April 16, 2014 3:54pm| By Greg Johnson
The NCAA Playing Rules Oversight Panel, which met via conference call Wednesday, approved a new football rule to better protect passers from low contact at or below the knee.
The rule specifically covers a scenario in which a quarterback is in a passing posture with one or both feet on the ground. In that situation, no defensive player rushing unabated can hit him forcibly at or below the knee. The defensive player also may not initiate a roll or lunge and forcibly hit the quarterback in the knee area or below.