John J. O'Brien: Basic Wrist Lock

John J. O'Brien is the man reputed to have taught Jiu Jitsu to President Theodore Roosevelt. In the pictures below -- from his book A Complete Course in Jiu Jitsu -- he demonstrates Katate Tori, the basic wrist lock.

If you practice with a friend, go slowly and apply pressure gradually. Have a prearranged signal to stop.