Unfortunately, in Temp Town, this is the kind of sign that actually is necessary. It ranks up there with "Please Don't Eat Other People's Food." This stuff happens all the time, on every project, because temps are animals, and so we get signs like this:
I wish this were the worst thing that happens on projects in Temp Town. It isn't. I get it, it happens in the real world, too, but not so often that building management feels the need to put up a sign. I'm still waiting for a sign in the bathroom that says, "Please do not take a dump on the floor. Use the toilet." Three projects and counting that needed that sign, and one of them was this year. Never underestimate how low temps will sink when it comes to failure to observe socially acceptable norms.