: if all door locks are different and different keys open different locks, how does a universal key work?
In: Engineering
In a normal lock (no master key), there are multiple pins along the length of the key that are split in two at different positions, corresponding to the ridges on the key.
When the key is inserted, the ridges lift the pins up and all the breaks in the pins line up along the edge of the lock body, allowing it to turn freely.
For a master keyed lock, each pin is split into three pieces, so there can be a continuous line of breaks in two positions (technically more than two, but unnecessary detail). That means two different keys will work in the same lock.
By having one set of splits in the pins in the same position, but the others in different positions, you can make locks that all open with the same master key but have unique regular keys.
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