This is a nice little door knob and door plate set - pretty easily available, these came from Dolls House Emporium. I always like door knobs with a screw thread fastening one to the other. The usual kind with a short stem on the knobs often need a bit nipped off their stems because when you shove the two of them into the drilled hole they prove too long for the thickness of the door and won't lie flush.
Fitting them - decide where the knob should go - check the ones in your house as a guide and/or research where they went at different times in history and on different style doors. I am nothing if not pernickity about these things. Mark the position with a pencil and hold the plate in place, keeping the hole for the knob over the pencil mark.
You can now make marks through the screw holes in the plate and a larger mark through the keyhole. Take the plate away and colour round these marks. I colour the screw holes with gold felt tip and the keyhole with black permanent marker. They are done over-sized to be sure no white wood shows round the edges of the holes when the plate goes on.
|top and bottom marks for screw holes|
Put tiny bits of superglue on the door between the marked areas. Thread the plate on the rod which has been screwed into one of the knobs and set it all in place. Keep everything spot-on vertical. Finish off with the addition of the plate and knob on the other side. I do believe you can get screws small enough for these holes if you want to seek them out but the gold finish underneath does a good enough job at a distance.