14-May-2012 One valve extension we CAN put a 1/4" square hole into - the water bypass handle extension. We've drilled a 1/4" hole in the stock and using a square file, put corners into the hole. The slot in the stock fits over the existing lever-handle on the valve. Here I am getting ready to drill and tap a 10-32 threaded hole for a setscrew. Easiset way to align the hole to the flats--let the square file key it for me!