I have bought a single antique brass door knob from a junk shop, which I would like to use. However, although it will take a standard square section spindle there is no way to attach it to the spindle. Instead it has a screw thread on the outside of the shank, obviously intended to fit into a rose, and I need to find a rose which will take this. There is no other way to attach the knob to the spindle, no hole for a grub screw or similar. I am familiar with knobs which have a screw thread on the inside of the shank and go onto a threaded spindle, but I have never seen one like this before. Does anyone know where such a thing could be obtained? Alternatively I suppose I could drill a hole for a grub screw, but I'm reluctant to risk spoiling it.