I found a glory hole once in a rest stop. Wasn't very big, but curiosity got the best of me, it was late and quiet so I pushed my soft cock and balls through the hole. The cold on the back of my balls made me hard fast...then it happened. I got stuck. I could not get my balls out with a hard cock, I had to stay still and let it soften. As soon as it was soft enough I pulled out fast, felt like I was going to tear off my balls. I was so scared someone would come in and find me like that.
Never seen another hole again since.