If you’ve ever thrown a party, you know how effective signs can be. They’ll help direct people to the appropriate beverage station. They’ll keep people away from the door to your parent’s bedroom. And they might just help people realize there’s a cat behind that door and if you open it all manner of chaos will be released upon this house. A quick use of a sharpie, a piece of paper, and some scotch tape will help prevent that. 

But, if you’ve ever thrown a party, you also know that people are equally adept at completely ignoring signs. They will see what they want to see and immediately photoshop it out of their minds, and then go ahead doing whatever they were going to do in the first place. It’s one of the great human flaws. But the signs in this list… might be fine to ignore anyway. Unless you want to end up in a wacky situation. Then go ahead.