The shaping of a wedge's sole — material ground away from the heel, toe, or trailing edge to change how the club interacts with the ground. Grind matters because bounce isn't one number in practice: a heel-relief grind (like Vokey's M) lets you open the face for flop shots without the leading edge popping up off the turf, while a full, wide sole (like the K) keeps maximum bounce for bunkers. Pick grind based on how you like to manipulate the face — open-face artists want relief, square-face chippers want full soles.