When I went for circumcision, they gave me the stockings, two gowns and a pair of these.
I put the briefs on, when stretched, they have a really mesh appearance, and the stockings and the two gowns, first back open, then front open over the top, as instructed.
When I walked into the OR, I took off the top gown, and laid down on the bed so the back open gown draped down and I guess they could lift it easily. They put ecg leads on the top of my shoulders, inserted the IV and off I went.
I was really surprised that when I woke up in recovery, I still had the briefs on, pulled back up, with my bandaged penis inside them. They're pretty fragile, it must have been tricky to pull them back up - I guess they didn't lower them much! It probably helped to keep everything in place
I did then of course keep them when I got dressed and changed to leave the hospital later that day, still have them!