This information was originally published on jiu-jitsu.net. It is made available on BJJ.Org by the express permission of featured contributor Gene "Aranha" Simco.
1. In this frame I (Gene) have already taken my opponent's (Joe) back. I have one arm under his arm, and one arm over is shoulder. He is creating downward pressure on my left arm, so I can not put my hand behind his head to complete the most basic choke from this position. So I have chosen to grab both of his collars (as shown) with one hand just below another, my right hand touching his neck & NO SLACK on the collar around the back of the neck. *note - My 'hooks' are in, and my ankles ARE NOT CROSSED.
** In Sport Jiu-jitsu the act of 'taking the back' with the hooks in is worth 4 points.
2. To create enough pressure on his neck to complete a choke. I make the 'wring the towel' move with my arms, turning my wrists out, and straightening my arms as I lean back.
3. In this next frame, Joe has removed my left hand from his collar, and trapped my arm under his arm pit.
4. I trap his arm with my left leg, keeping my foot tight to his body & on the floor.
5. Now I can push on the back of his head (or neck - there is more leverage at times on the top of the head), as I pull my right hand to the right to complete another choke.
6. Here is that same choke from the other side. Here I am creating the pressure by sliding my hand down my wrist into the back of his neck. The detail that is hard to see in this frame is that I am getting leverage by turning my left wrist. As soon as my left pinky is tight against his neck, I turn my palm toward his neck. This turning of the wrist and straightening of the arm will create a great deal of pressure without using a lot of strength.