While you are going down on a girl that is lying on her back, you grab her legs and throw them over your shoulders and thrust upwards. This leaves the girl's head and shoulder still on the bed, while her butt is in the air and legs completely over your shoulders. The licking continues in this position.
Person 1: Hey man what did you do last night?
Person 2: I High Tide Clam Harvested the shit out of her
Person 1: Oh man that's pretty legendary, that move is known to be the hardest in the league