Craig Douglas posted this refinement of the Underhook and Bicep Tie clinch in knife defense at the Shivworks Alumni page here:
The Hook N Ties are my favored Enhanced Close Quarters clinch as they are conducive to many takedowns. Seeing this refinement Craig offered, I saw a great opening for combining knife defense with a leg sweep takedown based in the same body mechanics and postural manipulation this position provides.
Here they are:
Front and back views:
Some description on the mechanics from the back view, showing how the underhook and postural mechanics work: