Very popular cruise bar at the SoMa neighbourhood. It has a small semi-outdoor smoking area that turns into a sex room. It's the closest thing to a European-style dark room you will find in SF.
Thursdays nights are underwear night. It's not required, but a lot of guys do strip to their skivvies. There is a contest to see who is the hottest.
Smoking allowed in backyard patio (some action to be had there too)
Arrived around 11pm on a Thursday evening. Underwear party. Not mandatory but a large proportion of guys did clothes check their pants and shirts and enjoyed the evening in their boxers/jockstraps. Some bar boy go-gos , and a wet underwear competition at midnight (which I missed as I was busy out in the small backyard enjoying a smoke and a new friend :-) Busy when I arrived and slowly started to empty around 1245AM. Decent looking crowd. - mainly 30-45 yo. Entry $5 and small charge to check clothes. Friendly - a place where you could flirt and talk before making your move. Real nice place. Will be back. But bring lube/condoms.
The best of the San Francisco cruise bars, and it's still going strong after many years. Fun, friendly, partying crowd. Lots of hot guys. Great music. Always end up here when I visit San Francisco, and always have a blast.