Overview
Hiji ate translates as "monkey's elbow smash". Hiji ate is one of the reasons that we don't practice uppercut punches until brown belt level - this is a much more powerful alterative! It's primarily used to target the bottom of the jaw, but if you're rising from a low position such as a crouch or your knees, it can also be used to attack the sternum with devastating effect.
Technique
Start with your left elbow up in a striking position, and the right hand retracted to the waist in the usual position. Now simply raise your right elbow powerfully towards the bottom of your opponent's jaw. Be sure that your elbow aims for the middle of your body, rather than straight in front of your shoulder. Beginners commonly deliver this strike by starting with an uppercut and continuing up to finish with an elbow strike. This is wrong and weakens the elbow strike. As you lift your elbow, keep your right fist close to your right shoulder throughout the manoeuvre. As your arm lifts, rotate your right wrist one quarter of a turn towards you. Your right fist should end up beside your right ear with your palm facing your head. As you raise your right elbow to attack, simply retract your other fist to your left side, ending up with your palm facing upwards.