The 900 is a 2½-revolution (900 degrees) aerial spin performed on a skateboard ramp. While airborne, the skateboarder makes two-and-a-half turns about his or her longitudinal axis, thereby facing the other way when coming down than before. It is considered one of skateboarding's most technically demanding tricks.

• http://en.wikipedia.org/wiki/900 (skateboarding)
• Page 3 - Sides, H., 2004, Americana: Dispatches from the New Frontier: Anchor Books, New York, 450P.