I have a bunch of suited camlocks, I am thinking of putting them on some cupboard doors. They are the sort with a round barrel with flats on it, and a flattish nut behind to clamp themn onto the door. They have to fit closely into the mounting hole to prevent them turning while not unlocked. I have not got a tool for making such holes. I think I have seen a sort of metal plate with a close-fitting hole in in that you can fasten to the inside of the door, but don't know how to find them. What are they called?