This technique is used when your attacker throws an upper-cut punch to your stomach.
When your attacker throws the punch, block the strike with a left-handed downward block.
Take your right arm round the back of your attackers blocked arm and use your middle finger to hook round their elbow.
Pull your attackers elbow out to the side and place your left hand on the inside of their elbow. Upto now this is a standard elbow lock. You only need to have your little finger on the back of their elbow at this point.
Grab their wrist with your right hand.
Take your left hand off your attackers elbow and grab your own wrist. This is now a solid hold that makes it very hard for your attacker to move. You can now finish with a knee strike to the head.