The heel of the hand. The wrist is locked and firm in all attacks with the hand. This is one exception. With the fingers extended, bend the whole palm back in the same position as when pushing of leaning palm first against a wall. The palm in this manner makes a battering ram of your forearm. The natural seat of your palm fits perfectly under the chin of an opponent. When in close, aim an uppercut at your opponent's solar plexus or chest, the heel of the hand will sweep up in a natural arc. The heel of your hand, directly backed by the bones of your forearm, will connect with the impact of a rock. Close your teeth and try it gently on yourself.