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What is a cylinder lock? How to identify your door lock

11 min read
Silberner Profilzylinder (Doppelzylinder) mit drei passenden Zylinderschlüsseln am Schlüsselring vor weißem Hintergrund

You are standing in front of the front door, key already in hand, yet it still takes a moment for it to find its way into the lock. Almost everyone is familiar with this, especially in the dark or with shopping bags on their arm. But what kind of lock is actually in your door? In most houses and apartments in Germany, it is a cylinder lock. In this article, we will explain in simple terms what a cylinder lock is, what types exist, and how you can find out for yourself in just a few seconds which lock you have. This is also the most important question if you want to know whether our planned key-insertion aid might be suitable for your door later on.

What is a cylinder lock? The short answer

A cylinder lock is a door lock that operates with a so-called locking cylinder. The locking cylinder is the part you insert the key into. According to Wikipedia, it "usually consists of a housing and a rotatable cylinder core." When you insert the matching key, the core can be turned, and the lock opens or closes.

The special feature: The cylinder is a separate component that sits inside the actual door lock. If a key is lost, you don’t have to replace the entire lock, only the cylinder. This is exactly what the police recommend in their "Sicher wohnen" (Living Safely) brochure: "If you lose your key, replace the locking cylinder!"

How a cylinder lock works

Inside a cylinder lock are small pins, known as pin tumblers. Each of these pins consists of two parts, a key pin and a housing pin. As long as no key is inserted, the pins block the cylinder core, so it cannot be turned.

Your key has small notches on the edge or small indentations on the side. When you insert it, these notches push each pin to exactly the right height. If everything fits, the shear lines of the pins align, and the core can rotate. With the wrong key, individual pins remain in the way, and nothing moves.

This is why a cylinder key looks the way it does: flat, with a jagged edge or small round indentations. You can use this difference right away to identify your own lock.

A brief history of the cylinder lock

The idea is older than many think. American Linus Yale filed a patent for a round cylinder lock with four pin tumblers on January 29, 1861, followed by a version with five pins in 1865. The principle of his invention is found in almost every cylinder lock today.

The form that can be found almost everywhere in Germany today came later: In 1924, engineer Sylvester Wöhrle developed the first German profile cylinder at Hahn AG near Kassel. The Imperial Patent Office granted the patent on October 25, 1928. This invention became the standard that you are likely looking at on your own front door today.

The two shapes: round and oblong

When you look at your door from the outside, you only see the face of the cylinder, the small area with the slot for the key. You can identify the type of cylinder you have by its shape. For everyday purposes, it is sufficient to distinguish between two shapes.

The oblong cylinder: the profile cylinder

According to Wikipedia, the profile cylinder is "the most common form of security door lock used today." From the outside, it looks like a classic, textbook keyhole: a round part at the top with a narrower stem below. The shape is therefore oblong, taller than it is wide. The key slot is usually positioned vertically in the upper, round part.

Profile cylinders are standardized according to DIN 18252 and EN 1303. This means that the basic shape is the same for all manufacturers, and a profile cylinder can be replaced regardless of the brand. A base length of 30 millimeters per side is typical, often specified as "30/30." For thicker doors, there are longer versions, usually in 5-millimeter increments.

Profile cylinders are available in several variants:

  • Double cylinder: It can be operated from both sides with a key. This is the most common variant, for instance on front doors, apartment doors, or basement doors.
  • Half cylinder: It only has one key side. You can find this, for example, on garage doors, switches, or cabinets.
  • Knob cylinder: Features a key on the outside and a small turn knob on the inside, allowing you to lock and unlock the door from the inside without a key.

The header image of this article shows such a double cylinder from the side, as it looks when removed. Inside the door, you will later only see the small face with the key slot. The keys next to it are typical cylinder keys with a jagged edge.

The round cylinder: the round cylinder

With a round cylinder, the face is simply circular. From the outside, you see a round disk with the key slot inside it. Round cylinders are the older design; Linus Yale already developed a round cylinder in 1861. According to Wikipedia, they are "hardly in use anymore" in Germany and are considered obsolete. Nevertheless, they still exist, for example on older doors or in other countries.

Important for you: A round cylinder is also a cylinder lock. It works on the same principle with pins and a rotatable core; only the external shape is different.

Not a cylinder lock: the warded lock

Many interior doors in apartments have a completely different lock, the so-called warded lock. According to Wikipedia, it is "a simple door lock, which is mostly used in interior room doors."

You can recognize it immediately by the key: it has a round shaft and a small, flat "bit" at the end, which often looks like a C, S, or Z. There are around 70 common bit shapes, which is where the name comes from. The keyhole has the same shape as the key, often a round hole at the top with a slot below it.

A warded lock is not a cylinder lock. It has no cylinder, no pins, and no rotatable core. It is also not intended for exterior doors, because according to Wikipedia, it can often be opened with a simple lock pick or a bent wire. For this reason, cylinder locks are used for house and apartment doors.

How to find out which lock you have in 30 seconds

You don't need any tools or expert knowledge for this. Just take a look at your key and your door.

Step 1: Look at your key

  • Flat key with a jagged edge (like a small saw) or with small round indentations on the surface: This is a cylinder key. You most likely have a cylinder lock.
  • Round shaft with a flat bit at the end: This is a warded key. You have a warded lock or another type of bit-key lock, i.e., not a cylinder lock.

Step 2: Look at the lock from the outside

  • The surface with the key slot is oblong, round at the top and narrower at the bottom: This is a profile cylinder, the oblong shape.
  • The surface with the key slot is circular: This is a round cylinder, the round shape.
  • You only see a keyhole in the shape of the key, without a separate component inside: This is usually a warded lock.

Step 3: Consider which door it is

In Germany, front doors, apartment doors, and basement doors almost always contain a profile cylinder. For interior room doors within the apartment, it is often a warded lock. So, if you want to know which lock is in your front door, the answer is, in all likelihood, a cylinder lock in an oblong shape.

Still unsure? Place your front door key next to the header image of this article. If it looks like the keys there, flat and with a jagged edge, you most likely have a cylinder lock.

Good to know: How far should the cylinder protrude?

If you are already standing in front of your door looking at the lock, a second glance is worth it. In their "Sicher wohnen" brochure, the police recommend a protective fitting according to DIN 18257. With such a fitting without a cylinder cover, "the profile cylinder must be flush with the protective fitting on the outside (maximum tolerance plus/minus 3 mm)." If the cylinder protrudes significantly further, it can be attacked more easily.

For everyday life, this means: A cylinder that protrudes only a few millimeters from the fitting is the standard for well-secured doors. If you are unsure whether your door is sufficiently protected: according to the brochure, you can "receive free and neutral advice on security measures from experts" at police advisory centers. You can find contact details at polizei-beratung.de.

What this means for our planned key-insertion aid

At Oxionix, we are currently developing a key-insertion aid. It is designed to help the key find its way into the lock without long searching. The product is still in development, and details may change before launch. What is certain so far: the insertion aid is intended for cylinder locks, both in round and oblong versions.

For you, this simply means:

  • You have a cylinder lock in an oblong shape (profile cylinder)? Then you belong to the group for which we are planning the insertion aid.
  • You have a cylinder lock in a round shape (round cylinder)? A version is also planned for this.
  • You have a warded lock or another bit-key lock? Currently, the insertion aid is not intended for these.

Whether the insertion aid will ultimately fit every single door, we cannot yet promise, as it has not finished development. If you would like to stay updated, tell us what is important to you in our short pre-launch quiz. As a thank you, you will receive early access at launch and a 10% discount on your first order.

Frequently asked questions about the cylinder lock

What is a cylinder lock?

A cylinder lock is a door lock with a locking cylinder. Inside this cylinder are small pins that only the matching key pushes to the correct height. Then the cylinder core can be turned, and the door opens or closes.

How do I recognize if I have a cylinder lock?

The easiest way is by the key: A cylinder key is flat and has a jagged edge or small indentations. On the lock, you will see a separate small surface on the outside with a key slot, which is either oblong (round at the top, narrower at the bottom) or circular.

What is the difference between a profile cylinder and a round cylinder?

Both work on the same principle. The difference lies in the shape: the profile cylinder is oblong, with a round top part and a narrower stem underneath. The round cylinder is circular. In Germany, the profile cylinder is the standard shape today; round cylinders are mainly found on older doors.

Is a warded lock a cylinder lock?

No. A warded lock has no cylinder and is opened with a warded key with a round shaft. It is usually found in interior room doors and is not intended for exterior doors.

Do I have a cylinder lock on my front door?

Most likely, yes. According to Wikipedia, profile cylinders are almost the exclusive design for security locks on doors today. A quick look at your key and lock, as described above, will give you certainty.

Is the Oxionix key-insertion aid suitable for my lock?

The insertion aid is planned for cylinder locks in round and oblong shapes. If you have such a lock, you are in the target group. The product is still in development, which is why we cannot yet guarantee a fit for every single door.

When will the key-insertion aid be available for purchase?

There is no fixed date yet. Those who sign up via the pre-launch quiz or by email will be the first to know when the time comes.

Sources

Image credits

Header image: "CES-Zylinderschloss mit Schlüsselsatz" by VSchagow, via Wikimedia Commons, license CC BY-SA 4.0, used unchanged.