OK, a followup. A problem. The precision adjuster slides onto the extension rails and the center screw threads into the metal casting that holds the fence. This screw must be captive to work. Mine would only work in one dorection; moreover, it fell apart. Close inspection showed that the very small locking ring that fits into a groove is missing.
A couple of emails with Lee Valley, and a couple of locking rings are en route via Fed Ex. Quick solution on their part.
