The triangle choke is a choke with your legs from the bottom. Fights end because of this submission all the time, and the beautiful part is that every step in the sequence locks the door behind you. Your opponent never gets a window to escape if you do it right.
Start from the triangle setup position: one leg up on the shoulder, one arm in, feet crossed. From here, it's a cascade. Step one — pass the trapped arm across his face. Lift your hips, grab it, shove it across. Confirm that grip with the same-side hand.
Step two — hold his head. Don't release the arm pass early. That leaves the door open. Once you've got the head controlled, put your foot on his hip and wiggle north. Scott is specific about this. If you're too deep underneath the guy, the finish requires flexibility most of us don't have. Scooting north fixes the angle.
Now bite your calf across the BACK OF HIS NECK. Not his back. Horizontally across the neck. This is the mistake everyone makes. Grab your foot to confirm, then pass the other leg over so it locks into the crook of your knee. Leg, leg, leg. That's the triangle.
The finish is three things at once: squeeze your knees together, pull his head down, lift your hips. All three. Miss one and the choke leaks.
Practice this sequence at home on a pillow if you have to. The steps should become automatic. For the full triangle system with multiple entries and setups, check out our triangle choke setup system guide. Get the full course in the BJJ 101 System.