I had a FWB, who's office overlooked a very busy pedestrian street. His office was on the ground level and had this massive floor to ceiling window. But the window had this 1-way privacy film/treatment on it. So those inside could see out onto the busy sidewalk, but those outside could not see in.

Often times, I would meet my FWB at his office, and fuck against this window. A favorite position was standing doggy. Where my legs would be spread wide, my face pressed against the glass, and he was behind me pounding away. It was surreal experience to see the pedestrians walk on the sidewalk, unaware of my debauchery only inches away. Being completely nude, being fucked, while relying on this thin piece of privacy film to protect me was simply exquisite.

I'm a very vocal woman during sex. So often I would moan or scream. So there were a number of times when a person standing outside the window would turn around and face the glass. Probably overhearing my squeals. Or they would notice the sounds, the cadence, the rhythm of the pounding against the glass.