This choke is used when your opponent is pushing on your chest whilst in the guard, maybe trying to stand up.
Bring both arms inside your opponents arms ready to push them aside.
Take your arms to the side and up, this will slide your opponents arms off your chest.
As your opponents head falls, wrap your right arm around the back of their neck and grab your left bicep with your right hand.
Now slide your left hand under their neck. You may use a scissor hand or a fist to crush your opponents throat. Push your left elbow down and your left hand up into their throat.