I often have to work on weekends. When my body is demanding some attention that it's not getting from writing reports on a Saturday afternoon, I have sometimes gone to the largest stall (the wheelchair-accessible one) in the men's room on my floor, closed the door, dropped my pants and masturbated there.
I have a recurring fantasy about being stripped from the waist down, in front of an audience, and masturbated to orgasm while they watch. The large amount of space around me in that stall supports that fantasy. Sometimes, other staff come into the restroom while I'm in there, and if they're talking, that supports the fantasy, too.
In that location, I masturbate by stroking and rubbing the point just below my glans, which often brings a very intense climax, without any telltale slapping sound to give me away. I have often thought that anyone paying attention would notice that it's a little unusual that I am standing in there with my pants down and my feet pointing toward the toilet, instead of away, but that just adds a little to the feeling of risk.
Sometimes, one of the female custodians works on Saturday afternoons, too... and she has made no secret of the fact that she would like to see my penis. She has asked me about this repeatedly, and thinks I must be huge because I wear size 12 shoes (which is nonsense, of course... I'm a little longer than average, it seems, but not enough to quit the day job)...
So she has sometimes "accidentally on purpose" followed me into the restroom and hollered from the doorway, "Are you back there, sir? Is it OK if I clean in here?"
The lady has never actually tried to pull open the door to my stall, but on a few occasions, she kept talking with me, and I talked with her, while she was "cleaning" the outer portion of the restroom, and I was silently stroking... and she became a part of my fantasy.