There’s a lot to be said about the triangle choke. For one, it’s the most effective submission out there. It can catch you out of nowhere and even if you don’t put your opponent to sleep you’re still controlling them. The Gracie family, who are incidentally the founders of Brazilian Jiu-Jitsu, patch their GIs with a triangle for a reason.
Alright, you’ve got a couple of setups down. You keep catching a head and arm, but you can’t finish it. Partner won’t tap. Give this video a look.
Finishing the triangle is easy. Trapping the head and arm, that’s where you’re going to run into the most resistance. Alright, you’ve managed to lock guard around a head and arm. Grab the shin that’s on top of your partner’s head with the cross-arm. Put the other heel or ball of foot onto partner’s hip. Underhook partner’s leg or arm with free arm. Rotate using the heel on hip. Your lower back should be your axis. If you’ve got your weight centered onto your shoulders the rotation is going to turn into an awkward shoulder walk. Keep your axis on your lower back. You’ve rotated. Your head is close to the underhooking shoulder. Adjust the biting leg so that it bites into the neck at a 90 degree angle. Get your foot off the hip and lock in the figure four.
You’ve figured it out. You squeeze by bringing your knees close together. On a larger opponent the knot or noose is tight and bringing your knees in will make his head explode. Someone smaller, however, might just pull their head out when you do this. Try this instead. The leg that’s got a bite on the neck is actually doing the choking. That’s what you’re going to focus on. Use the figure four to close your biting leg, looking to bring the heel as close to your butt a possible. Now for the pro-tip, if the noose is too loose, lock the triangle, not instep-below-nee, but ball-of-foot below knee. Don’t break your big toe. Flex your foot. Good luck.