The ulna is the bone that runs in the forearm on the side of the arm your pinkie finger is on. When executed properly, your bent elbow will be in a 90 degree angle from your shoulder. It will be above and slightly in front of your head. The blocking surface once again is the ulna. It should be level across the top from your elbow.
Fist is tight with fingers facing outward and forearm is taunt.
As you get used to this upward snapping movement that passes over the other arm, start bringing the other fist down and level with the side of your belt. The elbow will be sticking out behind, your forearm and fist will rotate up so the fingers are facing towards the sky. From this, the fist at your waist can then deliver a strong, well placed punch after you have blocked your assailant s attack. This block and retaliatory strike should be practiced repeatedly until you are comfortable with them and then practiced some more. If you have to pause to think how to execute a block, the attack will be over long before you make your first move.