Forget T-rails and 1/4" or 5/16" screws. This makes it easy to install a built-in clamp for any jig or fixture. I used a Freud 1/2" 14 degree dovetail bit. Make sure the bit is 3/8" tall and the clamps work like a champ. So far I've been using them as the clamp for my desktop router table, when Stop block for my bandsaw and table saws This is really a brilliant innovation I'm taking off one star because of the price They should be $25-30 for wider distribution.