Rear naked choke

The rear naked choke or "Mata Leao", when properly applied, is probably the most devastating technique in Brazilian Jiu-Jitsu. It has been used to gain victory in numerous mixed-martial arts/NHB events, such as the Ultimate Fighting Championship or the Pride Fighting Championships. In fact, the rear naked choke is so effective that using it in any situation, practice or otherwise, is illegal in some areas.

The rear naked choke is poorly named, as it is not an actual choke but rather a strangle(the difference between the two is that a choke cuts off the supply of air to the lungs, while a strangle cuts off the supply of blood to the brain). By blocking the carotid arteries, this strangle can render an opponent unconscious in as little as 10 seconds. Hence, when practicing the rear naked choke, as it will be called despite the fact that it actually a strangle, it is extremely important that one lets go immediately after the opponent submits. Otherwise, you could wind up with a wrongful death lawsuit on your hands, which would be a very bad thing.

1. By far the most difficult step is getting behind the opponent(this is why it is called the rear naked choke). There are two ways to do this: One, sneaking up on them from behind when they aren't looking, or two, applying the skills and positional techniques of jiu-jitsu, if you aren't a coward and actually are taking part in a real fight.
2. Now that you are behind them, begin by sliding your thumb down the side of the opponents neck, and bring your arm around until the inside of the elbow reaches their adam's apple. By choking at the adam's apple, you ensure that you will not permanently injure the opponent by crushing their trachea. To actually strangle the opponent, instead of just putting them in a weak rear head lock, it is important that your choking arm be underneath the person's chin. Otherwise, you will be putting the pressure of the move on their jawbone as opposed to their blood vessels. After the arm is in place, take a step to ensure that it stays there by grabbing the bicep of your other arm. If you have a shirt sleeve, grab that too.
3. Now, using the the arm that is being grabbed at the bicep, place that hand onto the back of the opponent's head. Be sure to keep the hand somewhat low, near the back of the head/medulla area, as opposed to on the top of the head- otherwise the opponent will be able to reach up and pull it off. To finish the manuever, bring the two elbows together. Again, remember to let go when they say, unless they did something really bad, like sleeping with someone else's lover.

Since it can be hard to visualize what a rear naked choke is from words, you can follow this link to see a picture of Royce Gracie using the maneuver on Ken Shamrock. There are also plenty of movies of people using the manuever at sherdog.com, but providing a direct link to movies is just stealing, so visit the site and look around if you want to see those.