Achilles tendon
Executing this lock involves pressing the achilles tendon into the back of the ankle or lower leg. It is typically performed by wedging a forearm, especially a bony part of it, into the Achilles tendon. Simultaneously leveraging the foot and the leg over the forearm, which serves as a fulcrum. This causes severe pressure on the Achilles tendon, often resulting in an ankle lock, since the ankle is being used as a point of leverage. Similarly, some ankle locks also cause a compression lock on the Achilles tendon, and hence the term "Achilles lock" is often also used to describe such ankle locks.