This may look like an April Fools' Day sign, but in fact, it is not,
and can be found on many elevators here in Sweden.
This "squeeze risk" comes from not having a door as part of the elevator, so you can reach your hand out and touch the wall as you go up or down. Unfortunately, this missing door can wreak havoc if you happen to have a large item, say a trash can, with you in the elevator. Don't become the victim of this unfortunate calamity - take the stairs!
On that note, I'll leave you with the Swedish April Fools' rhyme>
April April din dumma sill,
Jag kan lura dig vart jag vill!
which literally translates to>
April April you dumb herring,
I can trick you where I want!