The first thing that struck me in Berlin was the Berlin key, “I can’t imagine such key exist on earth.” The Berlin key is also called “Schließzwangschlüssel” or close constraint key. It is a very specific kind of key lock and is a distinctive feature of the city of Berlin, Germany.


The key particularity comes from its two key tips (the part which activate the bolt). After unlocking the lock, the key must be pushed through and retrieved on the other side of the gate to close this latter. This key was actually designed to force people to lock their gate (usually a front door or gate). The mechanism makes the retrieval of the key impossible once the bolt is unlocked, the gate must be locked again in order to extract the key. With this type of key lock system, “locking” the door while the door is open is normally not possible. However, couple of times I saw the gate opened without the key stuck in. I don’t knowhow they do it.

Invented by the Berliner locksmith Johann Schweiger, the key was massively produced by the Albert Kerfin & Co company starting in 1912. Nowadays this kind of lock is disappearing but still is one of the typical object from Berlin.


I am not only fasinated by the key but also its keychain system designed to hold the key.

(Text excerpt from Wikipedia)