Give Them The Finger(lock)

Ah, you gotta' love old Wally Jay.
There are obviously universal qualities that all grappling arts share, but Wally Jay and son Leon have really refined joint locks with "Small Circle Jujitsu".
Our fellow Dojo Rat Corey trained with the Jays in London and again back in the Midwest along with George Dillman. I met and trained briefly with Leon in Portland. Small-Circle Jujitsu is a perfect compliment to the Aikido and Chin-Na I've done, and the flow drills ease the transitions between techniques in a resisting opponent.
Look at the finger locks Professor Jay uses on the student in the video. Done correctly, I have not met anyone that will not react to a finger lock in a very predictable way. It is something a small person can apply to a much larger person, from a variety of angles.
Now, nobody carries on like in the video above, the finger lock is intended to cause pain and distraction in an opponent while you line up a knockout technique.