This knuckle is used from a semi-closed fist, and is meant to pinpoint pressure points. Strongest if delivered straight in or at a downward angle.
KNUCKLE 4 - the 2nd knuckle of the middle finger.
This knuckle is used from a semi-closed fist, and is meant to pinpoint pressure points. Strongest if delivered straight in or at a upward angle.
KNUCKLE 5 - the head of the ulna located at the wrist.
This knuckle is used only from a closed fist. It can be used as a strike or a block (middle block). Like knuckles 3 & 4, this knuckle is thought of primarily as a pressure point strike.
The GOJU-SHOREI FIST.
The picture of Knuckle 6 illustrates the preferred structure of the fist. The last 3 fingers of the hand (from little finger to middle finger) are folded normally. The index finger is held straight from the 2nd knuckle to the tip of the finger. The thumb wraps over the index finger tightly which compresses the metacarpals of the hand. This fist structure also prevents hyper-extension of the wrist when striking.