The Triangle Choke is commonly used in both Judo and Brazilian Jiu Jitsu as well as being a popular chokehold in MMA. The application shown from this instructional video is of the hold being implemented when you have your opponent in the guard position. You encircle their neck with one of your legs, your knee being at a right angle, entrapping their opposite arm at the same time. You position your other leg over the top of the ankle of your bent leg reinforcing the hold by locking your limbs into a triangular shape. You can then apply additional pressure with your free hand pulling the back of their head toward your body. This constricts blood flow to the head and makes breathing difficult inducing the submission from your opponent.