Hello, I was wondering if anyone could help me identify a piece of hardware. It is from a support rail on an Ethan Allen ladies' writing desk, used to pull the rail out. It only had one when I bought it. I can't seem to find anything like it anywhere! I tried to upload a picture but it wouldn't let me. It's a small, screw-in knob. Does this have a specific name?? And where could I buy these?