Don't really understand this - some of the slaps are clearly just with the tips of the fingers and very top most part of the hand. The one with the brutal knockouts are basically just open-hand fists, hitting with the bones of the hand. If you tilted your hand silghtly so the bottom edge was facing out, you would basically be knife-hand striking people in the chin/neck. You can break boards with knife-hands, its one of the harder parts of the hands to use in strikes.