Once upon a time, I used to visit a "cottage" in West London where there were gloryholes between the three cubicles.
I was in the one in the middle; to my right a guy was havig a quiet wank which was nice to watch and quite a turn-on. After a while a guy came into the one to my left. When he sat down I could see through one of the gloryholes that he was wearing a red silk basque with black lace trim. He sat and played with himself for a while and must have noticed that I was wanking as well - he stood up and I noticed that he was beckoning to me through another hole that was about cock height from the floor.
I assumed that he wanted me to put my cock through the hole so that he could wank it for me. My cock did the thinking and I stood up and put my now very hard cock through the hole. I'd done this before so I knew how it would feel if he took me in hand or if he sucked me.
However, this was a very different sensation - something quite tight and warm had engulfed my cock. I realised that he had got into position and pushed his arse onto my hard cock. Without realising, I was buggering my first guy! He was good and this was obviously not the first time he'd done it. All I had to do was push my cock as far through the gloryhole as I could and he did all the rest; sliiding on and almost off my really throbbing, hard cock. I held on for as long as I could but eventually had to shoot my load. He must have thought it was a hosepipe up his arse I came so much. He held me in place as long as he could, gently squeezing the last drops out of my cock but eventually it lost its hardness and we separated.
Both of us sat down so as to clean up. I left then and found that there were several guys waiting to use the cubicle after me. I wonder how many cocks he managed to take that session. Sadly I never saw him there again although I always kept a lookout for what I thought was probably his Rover car.