Figure-four leg lock

Figure-four leg lock is a descriptive name for the body triangle — the back-position leg configuration in which the attacker crosses one leg over the other behind the opponent’s torso, hooking the foot behind the opposite knee to form a closed figure-four loop.

Etymology. The “figure-four” descriptor flags the geometric shape of the leg configuration — the same figure-four geometry used in figure-four grips on the upper body (kimura grip), applied here to the legs around an opponent’s torso. The “leg lock” suffix marks the closed-leg pattern as the controlling structure, even though the configuration is a positional hold rather than a joint submission. The label predominates in older no-gi instructional vocabulary; “body triangle” is the standard contemporary term.

Mechanics. The closed figure-four creates a segmented constraint around the opponent’s torso — the attacker controls the opponent’s hip area separately from the upper body, preventing coordinated escape rotation. The connection through the closed leg loop is what makes the back position retainable against a resisting opponent.

Cross-reference. Modern no-gi vocabulary uses “body triangle” predominantly; “figure-four leg lock” remains current in coaching contexts that emphasise the geometric shape. Full mechanical coverage on Body Triangle.