I don't actually know what the official phrase is (the term of art), but I bet there is one -- a practice in a system that the users create on their own, independently from the creators or maintainers of that system. Several weeks ago, someone had mentioned to me that users of the bike share program (which is found internationally and across the US, here's the NYC site) would, upon returning a bike that had a problem, reverse the seat. This acted as a sign to other users. This was not official, and somehow had to spread in terms of knowing what it meant (perhaps via forums). So I don't know all the details, but I finally saw one at the rack outside my office! (And no, this is not a staged photo -- I could have done that but where's the fun in that?)
