Despite my age, my experience is somewhat limited. For example, in real life I've never had sex with a man, just a couple of near misses, for example...
About 50 years ago, 18 years old and horny as hell, I'd just finished my delivery round and went into a brick-built public toilet. I saw a hatch to the roof space and wanted to climb up and see if I could spy on the women. Embarrassing now, but I was young and alone... Anyway, it never came to that: beforehand, I wanted to check that there was nobody in the cubicles - well, one was empty, but as i pushed on the door of the other one, someone was in there and blocked it - neither of the cubicles had working locks. So, I went out and came back a few minutes later.
Tried the door again - he was still in there, and I was pretty sure what he was doing... That's not what turned me on at that age, I just desperately needed to wank, so I went into the other cubicle and let my pants down so i could grab my already hard dick, cup my balls and start tossing off. The door was at my right side as I stood facing the toilet bowl, and I had my foot blocking the door.
I heard him going out of the other cubicle and then unexpectedly he pushed against the door. I held it shut, but then he pushed much harder, barged in and closed the door again - he was standing next to me with his erect cock in his hand!