If you are not sure of the screw size on your item, take it to any hardware store, they have boards with all screw size holes so you can see the size you need. Cabinet knobs are either 10-24 or 8-32. The average trophy is 1/4-20. For antique door knobs you can use any of the stoppers with the 3/8-16tpi which is: SS-8000, SS-9000, SS-3000, the whiskey, bottle cap openers and tab lifters. If they don’t thread into the door knob, you can run a tap 3/8″ 16tpi tap into the door knob to recut the threads.