Bit lock

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Mature box lock (occupation lock) with tumbler key
top: snapper or lifting the case (a)
middle: locking spring (b) for locking
Bottom: key house (c), Night slide (d)

A tumbler lock is a very simple door lock that is mostly used in room doors inside the apartment.

Cunt locks get their name from the total of 70 common, “colorful” (in the sense of “diverse”) key shapes.

It is considered relatively easy to open tumble locks with a simple locking hook or a bent wire without a matching key . Use in external doors should be avoided.

The key of a tumbler lock consists of a round shaft and a key bit , the shape of which often corresponds to the letters C, S, Z, t and Σ in the normal or mirror-inverted form. These simple tumbler keys are easy to buy, it is sufficient to know the shape of the keyhole, which also shows the low level of security of these locks, but is also an advantage, as no complicated adaptations of a new key to the lock are necessary. For box locks, tumbler keys with a longer shaft are usually required than for mortise locks, as the key must reach through the entire thickness of the door.

If the beard is also provided with millings on the underside, it is called a Chubb lock .

The lock has a keyhole in the shape of the corresponding key. If a key can be inserted, most locks can also be opened with it; There is no second or more exact mechanism that checks the key shape. When the key is turned, its beard engages the teeth of a locking bolt and pushes it out or in from the lock in the direction of rotation of the key.

However, this does not apply to locks or keys with additional security features: If the beard is also slit on the side (crew lock) or has recesses (chubb or grooved key), appropriate locks in the lock decide whether the key can be turned.

As a further protective measure, the bolt can only be moved under certain circumstances if the key simultaneously pushes up one or more metal disks ( tumblers of the Chubb lock) at the upper point of rotation . If the key fits, but the beard is too short, the locking bar cannot be moved. However, this protection is not too effective against lockpicks either .

Tumbler locks are only suitable for interior doors without security requirements. Cylinder locks (e.g. profile cylinder locks ) should be used for security-relevant doors such as exterior apartment doors .

By a key lock to the security of a tumbler lock can be increased.

Today, tumble locks are mainly used as mortise locks .


  • Otto Lueger : Lexicon of the entire technology and its auxiliary sciences . Volume VII, Deutsche Verlagsanstalt, Stuttgart and Leipzig 1894–1899.

See also