Crooked grind - the skateboarder grinds across the edge of the box on his front truck
In skateboarding, grinds are tricks that involve the skateboarder sliding along a surface, making contact with the trucks of the skateboard. Grinds can be performed on any object narrow enough to fit between wheels and are performed on curbs, rails, the coping of a skate ramp, funboxes, ledges, and a variety of other surfaces.[1]
^Badillo, Steve. (2003). Skateboarding : book of tricks. Werner, Doug, 1950-. Chula Vista, CA: Tracks Pub. ISBN1884654193. OCLC53293560.