Not many things are as entertaining as a passive-aggressive sign alerting the masses that they are angering management. These signs are meant to send a message, and they certainly do just that. They express frustration and annoyance better than anyone could in person, and if they're anonymous, that's even better, because they can say whatever they want while also hiding behind the shield of a piece of paper and the closed door it's taped to.

Often, these signs are pretty hilarious, because when someone's frustration has boiled over to the point of making one, you know they've got something particularly memorable to say.

Below is a collection of landlords, bosses and places of operation that felt the need to communicate via notices that are displayed publicly. Hopefully, you never find yourself a target of a sign like this, but if you are, please share a picture of it with the rest of us, because we certainly love these. Here are 15 of our favorite passive-aggressive signs.