the arm wrench

anybody have good experiences/training tips/info/history on the arm wrench in wing chun, kali, mantis et al...

Im not sure I know what you mean by arm wrench?

Hard to explain....You see it alot on Paul Vunak's tapes and a bit on Matt Thornton's..

Basically, one forearm in on lower outside of opponent's arm, your other arm is on the upper inside just below the wrist. Both arms swing, one going one way, the other going the other way. The opponent's arm is caught in the middle and the elbow pops.

It is also used to set up HKE

Oh, I was wondering what you meant, too.
We used to do a similar move in HKD. I always worried about the arm rotating during the move and the elbow no longer being in place for hyperextension, because we weren't control the arm with a grip on the wrist/forearm.

If it's what I'm thinking of there's a story about a jujutsu guy who beat a boxer back in the early 1920s with this kind of lock in a match.

I'm still not seeing it...could you explain it again? How the guys are stading, left arm right arm...

Is it this move?