Ashi-garami (足緘), the entangled leg lock.

Kansetsu-waza (joint locks).
Required for: 3rd Dan (black belt, British Judo Association); 4th Dan (black belt, British Judo Association); 5th Dan (black belt, British Judo Association).
Also known as: leg entanglement (bjj) - BJJ keeps the name ashi garami for the position, the foundation of its leg lock systems, where entangling the leg is legal at advanced levels..

About
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A joint lock applied to the leg by entangling it, the classical example of why judo restricts kansetsu-waza to the elbow: knee joints give way without useful warning. Banned in competition and in randori; it survives formally in katame-no-kata, where it is studied under control.

Key points
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1. Recognise it: the leg entangled and rotated rather than the arm
2. Competition joint locks are restricted to the elbow; leg locks are prohibited
3. Studied only in kata under supervision, never applied live

VI judo notes
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Nothing here is practised, but the reason for the ban is worth carrying: a knee gives way without the graduated warning an elbow gives, and pressure you did not see arriving is pressure you start tapping to late. If a partner ever entangles your leg in randori and you feel load come onto the knee, tap at once rather than waiting to work out what it is.

Reference pages elsewhere
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Ashi-garami on the IJF technique reference (International Judo Federation): https://judo.ijf.org/techniques/Ashi-garami

From Waza Book: https://wazabook.com/techniques/ashi-garami/