I have a door that has a roller catch mechanism, I have bought a new mortice knob and I would like to know how to fit it so that know doesn't spin (if that makes sense) Normally the square type bolt would engage in the door latch so that when the knob is turned it opens but in this case the knob needs to be fixed as it is a roller catch. I plan to drill hole through the door but would like to know if there is a way to stop the knob spinning?