Many many times. Had my first experiance back in the 1970's when the "entertainment" of adult movies were shown by an 8 MM projector in a booth. I knew I could stick my cock through a hole cut in the wall between the booths and get a fantastic blow job. I progressed to returning the favor and quite enjoyed that also. As a young buck back in the early 1980's. One of my most memorable visits was when I started to get sucked then returned the favor. Then the man on the other side backed his ass to the hole. I began to have anal sex with him. It was fantastic as it was so much tighter than vaginal sex I had experienced. Needless to say I had a mind blowing orgasam. I got myself together and exited the booth the same time as him. I was shocked, it was my best friends father. He didn't know nor did I during the act who either of us were. It was somewhat embarrassing for both of us. I saw him many times afterwards at their house and neither of us mentioned it or repeated it.