
Berlin Key - woozyolliew
https://en.wikipedia.org/wiki/Berlin_key
======
Someone
The English description on that page doesn’t make it easy to understand what
this key does.

 _”Its name comes from the fact that it has two key blades (the part which
activates the bolt) at each end of the key, rather than the usual single
blade”_

How does that lead to the name “Berlin key” or either of the German names? I
would guess “Berlin key” comes from the fact that it predominantly is used in
Berlin.

 _”After unlocking the lock, the key must be pushed all the way through the
lock and retrieved on the other side of the door after it has been closed and
locked again”_

I think the main features are:

\- the key cannot be removed when the lock is open.

\- you can remove the key from the other side of the door from which it was
inserted.

It seems you can lock the door from the side it was unlocked from, and remove
the key from that side, too. You only have to push it all the way through if
you want the door closed and locked with you and the key on the other side of
the door.

I also think you can close the lock and remove your key when the door is open.

~~~
atoav
The Berlin key ("Berliner Schlüssel") was mostly used in tenements with
multiple backyard houses with a common front gate that should be closed at
certain times. These kind of arrangements were mostly used in Berlin, hence
the name.

The other German names for the key describe different aspects of it:
"Durchsteckschlüssel" translates to "push-through-key" and "Doppelschlüssel"
translates to "double-key".

If you are more curious about the thing, there is a book by philosopher Bruno
Latour on the Berlin Key where he describes the thing with the sociological
situation that lead to it if I remember correctly (was a few years ago when I
read it).

Edit: The basic idea is that in this kind of multi-party environment they
wanted to make sure the door is always locked in the evening (when people
return). To unlock the door you have to push the key through. Once you are
inside you can get the key back, but _only_ if you lock the door behind you.
So once the door is locked, it stays locked, unless someone from the inside
leaves it open on purpose. This way people cannot "forget" to leave it open.

~~~
eternalny1
Please contribute to the Wikipedia page, you seem to have some better
information than is there currently.

~~~
robk
It would be reverted immediately. Requires external sourcing.

~~~
imurray
The other names are already on the German wikipedia page:
[https://de.wikipedia.org/wiki/Durchsteckschl%C3%BCssel](https://de.wikipedia.org/wiki/Durchsteckschl%C3%BCssel)

------
cryptozeus
Video showing how it is used, really neat!

[https://youtu.be/UW4jZLEgaiU](https://youtu.be/UW4jZLEgaiU)

~~~
pzh
It seems that you can accidentally, or not, lock the door without fully
closing it, thus leaving it essentially unlocked, so the key isn’t quite fool-
proof.

~~~
coldtea
> _so the key isn’t quite fool-proof_

Yes, it's from another era, when the consumer was not expected to be a fool...

~~~
vinay427
That's one way to describe problematic design. In other words, the key doesn't
fulfill its intended purpose considering (as the comment you replied to noted)
one can do this either accidentally or not which can have little to do with
being a fool.

------
odiroot
I'm surprised some houses still use this. As it's impossible to leave the
building without a key in case of a fire.

I suspect it may even be illegal today.

~~~
esrauch
As an American living in Switzerland one thing that has consistently surprised
me is the difference in fire safety rules: not having any smoke alarm or fire
extinguishers in homes is common, and it's also common to be able to lock
people inside rooms/apartments/buildings so that they can't leave without
having a key. It's possible to lock someone in my apartment even if they have
the key if the door is locked with the key left in on the other side.

In the US if I checked out a rental home as a possible place to live and it
had any one room where you could lock someone in and they would be trapped I'd
wonder what weird shit happened there.

~~~
decebalus1
Don't know about Switzerland, but as an European living in the US, I think the
American fire safety rules are what they are mainly because most houses here
are basically matchstick houses built from prefab low quality wood which would
get devoured by flames in minutes. And the fire-resistant building materials
are super toxic when they actually burn. So fire is a very big deal...

Anecdotal, we had a fire in my building because the wrong type of lightbulbs
were installed in the hallways and because of their size, they were too close
to the drywall which in turn caught fire. So.. yeah. Matchstick.

~~~
_jal
I stayed in a house in Germany in which the walls were filled with dried-straw
for insulation. It was several hundred years old. There was a no-smoking rule.

~~~
atoav
> There was a no-smoking rule.

Which to be honest says not a lot about anything, because this isn't that
unusual in Central Europe.

Also: a lot of the old wooden houses are far better in terms of fire
resistance than you'd suspect on first glance, wood often outperforms concrete
and steel when it comes to structural integrity in a fire.

I don't know about the straw thing, I only know it mixed with clay.

~~~
_jal
The no-smoking bit was me being a bit, ah, dry. Sorry it didn't come across
better.

The home in question belonged to the extended family of my host family while I
was an exchange student. I went with them to a maintenance day and did
wallpaper. I got a very close look at the walls, not to mention the repeated
lectures on what a firetrap it was.

Trust me, it was.

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adrianmonk
This is super clever, but I bet some of its potential applications conflict
with egress safety requirements/laws.

(If a door is part of an exit route, you probably can't require a key to open
it.)

~~~
mongol
Makes me wonder: how are prisons handling fire safety?

~~~
novok
Cynically, probably through legal exceptions and active 24/7 staffing that can
double check fire alarms.

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barking
It's kind of confusing but easier to understand when you consider the primary
goal which is to force people to lock the door.

This is achieved by only allowing the key to be inserted or removed when it's
in the locked position. The push through is to allow them to lock the door on
either side.

1: it's a key that can only be inserted or removed when in the locked
position.

2: It can be only be pushed from one side to the other when in the unlocked
position

Therefore you can unlock the door on one side to let someone in, lock the door
on the same side and remove your key again. Alternatively you can unlock the
door then push the key to the other side, lock the door on the other side and
remove your key.

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aloknnikhil
[http://www.bruno-
latour.fr/sites/default/files/P-36-Berliner...](http://www.bruno-
latour.fr/sites/default/files/P-36-Berliner-KEY-GBpdf.pdf)

This is the original technical document on this key.

~~~
Sniffnoy
That is not correct. This is an essay by sociologist Bruno Latour about the
key, not a technical document.

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bigbaguette
On a side note, what is the rationale behind the fact that there are doors
that can be locked without a key? The horror stories of having the door
slammed and getting trapped while outside are so common. If a key was
necessary no matter what to lock a door, this wouldn't happen and people
wouldn't have to spend a kidney calling a locksmith in the middle of the
night.

~~~
Macha
In certain areas, the risk of forgetting to lock the door after returning and
having someone unwanted make their way in to the house is higher than the risk
of getting locked out after forgetting a key.

There is a larger group of areas where this is perceived to be true, even if
it isn't.

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mordechai9000
I suppose this is now superseded by modern locks, but this is a great example
of solving a problem with technology that would otherwise be left up to human
behavior. You could ask people to please make sure to lock the door, but there
would always be people who would forget, or just not care enough to bother.

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karmakaze
"Also, locking an open door is usually not possible."

A good feature to have on otherwise normal doors so that they only ways to
lock it is to be inside or outside with the key. I now have a greater
appreciation for deadbolts.

~~~
overcast
This is what I did when I moved into my house. Dead bolts only, and dummy
handles below.

~~~
allannienhuis
deadbolts can still have a key on the outside & a paddle-knob on the inside.
That's the normal case here in Canada.

~~~
overcast
Right, but I can't lock myself out with one.

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niklasd
I've actually came across this key in an apartment building in Berlin once, so
they really are still in use. The person living there did complain about it
though, as (at least in the evening) you had to collect guests from the main
gate and escort them back there when they leave, since using the key was the
only way to open it. Understandably this is quite annoying when you're living
at the fourth floor.

------
woozyolliew
Discovered via tweet:
[https://twitter.com/historyned/status/1178272006334242819?s=...](https://twitter.com/historyned/status/1178272006334242819?s=21)

Seems like an elegant, physical embodiment of resource acquisition, state
management, and release. Albeit uncomfortable in your pocket.

Comparisons to C++ std:: on some of these counts may be valid.

------
mpweiher
My house in Berlin, the Corbusierhaus[1][2], used to have this type of key for
the front (car) gate.

The gate was usually open, and then couldn't be locked with the key. If the
gate was closed, it could only be left again in the closed state.

The house is next to the Olympic Stadium, so the gates are closed when there's
a football game, concert or other event.

[1] [http://www.corbusierhaus-berlin.de](http://www.corbusierhaus-berlin.de)

[2]
[https://en.wikipedia.org/wiki/Unité_d'Habitation_of_Berlin](https://en.wikipedia.org/wiki/Unité_d'Habitation_of_Berlin)

~~~
pimlottc
A bit off topic, but how do you like living in the Corbusierhaus?

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Schmazo
I'm reminded of an old Weekly World News article in which a man tiring of
losing his keys so often took the drastic step of having a surgeon implant
keys at the end of of his fingers, so he could never lose a key again!

The photo they used to accompany the outrageous story was hilarious. Nowadays,
that doesn't seem as far-fetched of an idea, with somewhat similar futuristic
key implant methods becoming more readily available.

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pletnes
What is the closest crypto analog to this kind of key?

~~~
singron
I think it depends how you translate the locking analog. E.g. decrypting your
key with {gpg,ssh}-agent keeps the plaintext key in memory in the agent. If
the machine reboots or a timeout elapses, the memory is cleared and the key
has to be unlocked again.

~~~
alister
On-the-fly encryption, Truecrypt as the canonical example, has this property
too. The key is always in memory, decrypting text on the fly, but a reboot or
period of inactivity will wipe the key.

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adrianmonk
So Aldi shopping carts and Berlin keys are isomorphic.

You stick your token in, you gain access to a facility, and then to get your
token back, you must restore the facility to its proper state. Additionally,
in both cases, the facility you're unlocking happens to involve physically
moving an object around.

~~~
wongarsu
That's all Germany shopping carts, not just Aldi. Though I suppose Aldi has
the largest international presence.

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sebastianconcpt
_The mechanism makes it impossible to forget to lock the door, without also
forgetting the key in the lock. Also, locking an open door is usually not
possible._

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cyborgx7
My father lives in Berlin, and before his last move a few years ago he had one
of these for his house key. Never knew they were so specific to Berlin.

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pavel_lishin
> _The mechanism makes it impossible to forget to lock the door, without also
> forgetting the key in the lock._

Which I have done, multiple times.

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viburnum
Any sociologists want to summarize the Latour essay?

~~~
efls
I'll take a shot.

The subtitle of the essay is "Doing Words with Things", which is a reversal of
the famous essay of John L. Austin "Doing Things with Words". Austin pointed
out that words have practical effects. Consider the speech act 'I do', when
two partners marry: it are the words that have a specific effect in real life.

Now Latour claims that we -- philosophers, sociologists, but others as well --
have to pay attention to the effects material objects have on people
interacting with them. He claims that a specific _way_ of acting can be
inscribed in an artifact.

So the key is an example of this: you can only take your key out, if you lock
the door behind you. Rather than having a message next to the door saying
"Please lock the door behind you", this type of behaviour is enforced through
the artifact itself.

So social mores or norms can be inscribed in and enacted through material
objects (and not just through words).

At least that's an ELI5 version of what the essay intends to convey.

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Vaslo
Is there a technical analogue to this?

------
7373737373
[https://en.wikipedia.org/wiki/Mengenlehreuhr](https://en.wikipedia.org/wiki/Mengenlehreuhr)

~~~
simias
Why are you posting this? It doesn't appear related to the OP insofar as they
are both encountered in Berlin.

Also this clock design seems unnecessarily inefficient. Why divide 24 hours in
multiple of 5 hours instead of the much more natural 6? This way it would be a
lot easier to decode AM/PM.

I realize that it's about art more than practicality but I don't really
understand why that encoding was chosen.

~~~
nstom
I think it has to do with design. They wanted to make the two top rows have
the same amount of lights. Using 6 would mean one row of 6 lights and one of
4. 5^2 is the smallest square that provides enough values to fit 24 hours.

