I saw this in Wikipedia. Thought it was kind of ridiculous thats considered a grind.
Grinds are where a rider’s bike will slide along a surface (such as a rail, ledge or lip of a ramp) on a part of the bike other than the wheels. Usually “stunt pegs” are used; these are short tubes are attached inline with an axle that project out from the main frame so that they can slide along the surface they which grind. Some grinds also involve the cranks and pedals.
* Double peg: The rider must bunny-hop on and land both pegs on the rail or ledge (wheels must be off the ground for all grinds).
* Feeble grind: The most basic grind to do on a ledge. The rider must bunny hop and land the rear peg and the front wheel on the ledge. This is easy to do on a ledge because ledges are generally wider than rails.
* Smith grind: The step up from a feeble. The rider must bunny-hop and land the front peg and rear wheel on the ledge or rail.
* Luc-e grind: The rider must bunny-hop, turn the handlebars 45 degrees, and land the back peg and the pedal on the ledge and lean back, keeping the front wheel off the ground but not grinding the front peg on the top of the ledge either.
* UnLuc-e grind: The rider bunnyhops and lands the front peg and pedal on the ledge or rail, keeping the back wheel off the ground.
* Rollercoaster grind: The rider must find two rails or ledges close enough together so they can bunny hop and grind with at least one peg on each rail.
* Icepick grind: A rear peg grind where the rider is riding on the back peg only with the front wheel above the rail or ledge they are grinding on.
* Crooked grind: When alternate pegs are on either side of the rail.
* Predator grind: When the rider does a double peg grind on a rail then hops over to his alternate pegs.
* Toothpick grind: The rider slides on the front peg only with the rear wheel in mid air.
* Toothpick hangover : A toothpick grind where the rider hangs the rear end of their bike over the opposite side of the rail or ledge they are grinding.
* Parapalegic grind: When the rider jumps off of the bike, while holding your handlebars, and grinds the rail with his legs in an erect manner, pegs are not involved.
* tire grind: bunny hop and land both tires on the rail and ride it