I didn't get what sounding was until I looked it up on urbandictionary, but yes, I've seen advertisements that included pictures on fetlife and I agree, I don't get it at all. Probably because I want to touch the penis and don't want anything to get in the way with me touching it or blowing it. (edit: sounding is a form of BDSM, and the point of wearing it is to cause pain)

This is more of a side comment, but can you really feel the man's urethra with your tongue? Or maybe it is so small you can't really tell. I don't get it. =/ When I get a boyfriend it is gonna be my mission to find out.