Sankaku-jime (triangle choke) locks uke's head and one arm inside a triangle made by tori's legs. The neck is squeezed between tori's thigh and uke's own shoulder. In judo its signature entry is on the turtle, which makes it very different from the BJJ triangle choke set up from guard.
One triangle, three finishes
Before the mechanics, a coaching point. The judo triangle is not only a choke. Once your legs are locked around uke's head and arm, you have three finishes:
- Sankaku-jime itself, by squeezing your knees and pulling the head.
- An armlock on the trapped arm, stretching it along your stomach.
- A pin (sankaku-gatame), controlling uke on his back.
That matters in competition. If the choke does not go in, you keep the position and change the finish.
The turtle entry
Uke is on all fours. You are in front of his head, slightly off to his left side.
- Slide your right leg under his left armpit, shin passing in front of his neck from left to right. Your foot comes out the other side, behind his right shoulder.
- Grab his belt or his right arm to stop him pulling his head out.
- Bring your left leg over your right foot to close the triangle. The back of your left knee locks your right ankle.
- Roll onto your side and take uke with you. He ends up on his back, trapped in the triangle.
When the roll ends, you are on your side and uke is on his back, his head and left arm inside your legs. Now you can choke, extend the arm or pin.
The detail most people miss
The angle. If you close the triangle while lined up face to face with uke, it squeezes nothing and his neck slides out. Turn your body until you are almost perpendicular to him. As in BJJ, the angle makes the triangle.
A loose lock is the other trap. If your ankle is not deep in the back of your knee, uke pulls his head free as soon as you roll. Tighten before you roll, not after.
How it differs from the BJJ triangle
A Brazilian jiu-jitsu player usually sets up the triangle from closed guard. He is on his back with the opponent between his legs, waiting for one arm in and one arm out. His legs attack from underneath.
In judo you come from above, against someone defending in the turtle. The final shape is the same but everything leading to it differs. A judo player starting BJJ has to learn to attack off his back, which does not come naturally. A BJJ player coming to judo finds an entry rarely seen in his gym, and it works very well on the turtle.
Our view: the turtle triangle is under-taught in many judo clubs. It asks for flexibility and patience, yet it is one of the few attacks that threatens a tight turtle.
Defending as uke
Keep your elbows glued to your knees in the turtle so tori's leg cannot slide under your armpit. If it gets through, grab the foot and pull your head out before the triangle closes. Once you are rolled with the lock closed, put your free hand on his knee and turn your body toward his legs to ease the pressure. If it tightens, tap.
Safety and context
Sankaku-jime acts quickly. Uke taps twice and tori releases at once. Chokes are only legal in competition from the age set by your national federation.
The triangle fits neatly with the other turtle attacks. When uke guards his neck, okuri-eri-jime makes him defend the lapels and his armpits open for the triangle. When he guards his armpits, hadaka-jime becomes possible. On the trapped arm, the armlock finish follows the logic of juji-gatame.
All the ground techniques are gathered on the katame-waza and ne-waza page, and the Kodokan syllabus of throws is on the gokyo page. To build it, one session a week is enough: twenty entries per side on a passive turtle, then rounds where uke resists at half intensity.