A common occurrence at bear events (events for the husky, hairy gay man).
First you get sucked half hard by another attendee. Then that person guesses how far down your leg your cock will go and pins his club pin or some other pin to that spot. This is supposed to irritate the head and cause a wet spot on the pants.
Often an initiation for first time attendees
Bear: hey, did you hear what happened to Jim at TBRU?
Cub: Yeah, he got a Texas pinning the first night!