Designed for 1/4-20 hex nuts, these nifty T-Tracks make jig building easier, and allow me to make the jigs I build far more versatile. In fact, its easy to get carried away and build jigs that are much more versatile than they really need to be. Most T-Tracks require the use of special threaded nuts that slide in the track itself. These Incra T-Tracks accept standard 1/4-20 hex nuts (not included). The single T-Track recesses in a 3/4" x 1/2" deep groove and is attached from the top with supplied wood screws.