Paul demonstrates non-destructive entry on a Thumb Turn Lock. These kinds of locks are generally Euro Cylinders and are used on UPVC Doors. They allow you to use a key for entry on the outside while using a knob on the inside for ease of use.
They are more ideally suited for rear doors rather than front doors. This is due to security issues if you have a large letterbox in which someone can gain access to the knob and turn it.
If you do use these types of locks on a door with a cat flap or letterbox then its prudent to have some form of security cowl or cage.
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