At my previous office, the cubicle farm I was in was actually a large room with 2 glass doors, one at each end of the room.

However, we’d only bother to unlock one of the doors - the one on the left which is nearer the main department entrance. The other one on the right was perpetually locked.

Unfortunately, every now and then, some visitor would come and decide to enter from the locked door. They’d push the glass door, only to find it locked. Some morons had to push and pull and push and pull a few times before getting convinced that the door was locked. And every time the door was pushed (or pulled), it would cause a banging noise, disrupting our concentration.

One day I decided I had enough. I stuck a sign on the door.

Office door

Here’s a closer look:
BREAK GLASS IN CASE OF EMERGENCY

It helped a lot.

But after that, every now and then, some moron would still come a visiting.