A cleat is screwed to the back face of the front jaw. The cleat slides in a rabbet to hold the front of the tailvise level with the top of the workbench. I am testing the fit of the assembled vise, checking for fit and insuring that the threaded end cap has been trimmed back enough to allow the body of the vise to move without binding against the projecting end cap.

 

Assembly of the tailvise is a complicated process. The body of the vise can be attached to the bench top. But to install the guide bar that passes under the bench top and through a hole in the end cap, you need to unscrew that top and flip it over. Luckily I was able to remove the lag bolts holding the top on at the rear of the base with a socket and a ratchet with a long handle. A better idea would be to not screw the top down until after after installing the tailvise. I got ahead of myself there.