This sticker was seen on the door of the IT-faculty building of the University of Jyväskylä. The sign itself is not very remarkable, but what I found interesting in this one is how some signs can tell you a lot about the local area. In particular, this sign is something you would only find in a place with harsh winter conditions where using metal studded shoes is common enough to warrant such a sign.
Again a nice reminder of the fact that we tend to only create signs and rules which we presume might get broken; you don't see signs telling you to obey the rules of physics.