Aiyahl lock

An aiyahl lock was a Vulcan martial art move that was effective on both Vulcans and Romulans. It involved crossing both arms crossed over each other until they reached above the head. The goal was to restrict the blood supply to the head and would result in the individual going unconscious.

Spock used this move against tr'Nelle on Memory Prime when the Adepts of T'Pel arrived at the planetary library facility. (TOS novel: Memory Prime)