External doors should have British Standard Mortice Locks.
Not everyone has a UPVC or composite door. So how do we know that the locks in wooden doors are adequate?
Locks in wooden doors should be a minimum 5 lever British Standard Mortice Lock, and will be marked BS3621 and carry the British Standard kitemark. You should find these details on the faceplate as shown in the photo here. Another way to confirm is to measure the bolt, it should protrude at least 20mm when locked.
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