What is a British Standard lock?

A British Standard lock has been tested by an independent body to show it resists common ways of breaking in. Locks that pass carry the BSI Kitemark. These are the standards you are most likely to come across at home.

BS 3621

The main standard for locks on wooden doors, such as mortice deadlocks and nightlatches. The lock needs a key to lock and unlock it from both sides. It is the standard most home insurers ask for.

BS 8621

Similar to BS 3621, but it opens from the inside without a key, using a thumb turn. This makes it quicker to get out in an emergency, which is why it is often used in flats and rented homes.

BS 10621

A lock that can be set to work either way: needing a key from the inside when everyone is out, and opening with a thumb turn when you are in.

TS007

The standard for euro cylinders and security handles, used on most uPVC and composite doors. It uses stars. A 3-star cylinder meets the standard on its own. A 1-star cylinder needs a 2-star handle to reach the same level.

Sold Secure Diamond (SS312)

An independent test for euro cylinders that includes snapping, one of the most common ways uPVC doors are attacked. A Diamond rated cylinder is a strong choice for a front door.

Why it matters

A tested lock is harder to beat, and it may be what your insurer needs. Cheap unbranded locks can look the same from the outside but wear quickly or fail.