The clamping force on the extension is very light. The stock indexing rib on the bottom of the extension prevents it from turning. The clamping location relative to the vise location on the bench gives me 360 degree access to the receiver extension nut.
http://i1363.photobucket.com/albums/...ps43e6f187.jpg
http://i1363.photobucket.com/albums/...ps4ab007b1.jpg

