My ex used to have a small low stool with slot in the top rounded on the ends. I have no idea what it was for originally but she found out that if I sat on she could pull my cock and balls through the slot. Now she would place a cock ring on me and I was trapped on it as long as I was slightly hard. She called it her "milking stool " and used to torture the hell out of me on it.
When not is use it stood in the living room. More then once with her friends over she would look at it then at me and watch me blush