Around half the front doors our locksmiths attend still carry a euro cylinder that can be snapped in under a minute. That is not a scare line — it is the single most common weakness we find on otherwise solid uPVC and composite doors, and it is the reason lock snapping became the burglar's method of choice across the UK. The good news: it is also one of the cheapest serious security upgrades you can make, and you can check whether you need it in about two minutes with no tools.
This guide explains how snapping actually works, how to read the ratings that matter (TS007 stars and the SS312 Diamond), how to test your own door today, and the fitting detail that most articles never mention — the one that quietly undoes an expensive lock if it is got wrong.
A euro cylinder is the pill-shaped lock that sits through the handle of almost every uPVC and composite door in Britain. Its weakness is built into its shape: the cylinder is held by a single fixing screw through its narrow waist, right at the centre. Apply leverage to the part of the cylinder that sticks out of the door — mole grips and a bit of force are all it takes — and a standard cylinder breaks at that waist. Once the outer half is off, the cam that works the lock is exposed, and the door can be opened in seconds.
What makes this method so popular with burglars is that it is quick, quiet enough, and needs no skill. Picking a lock takes practice; snapping one does not. When our locksmiths attend burglary repairs, a snapped cylinder on the back or side door is the pattern we see far more often than any other.
Two independent schemes test cylinders against snapping, and both mark the passing locks so you can check at the door:
Either a TS007 three-star cylinder or an SS312 Diamond cylinder is a sound choice. Where homeowners get caught out is the one-star-plus-handle combination: it is legitimate, but only if the two-star handle is genuinely fitted and the pair stays together. Swap the handle later for a pretty one from a DIY shed and the protection quietly disappears. If you want one decision that cannot be undone by a future handle change, fit the three-star or Diamond cylinder itself.
Open the door and look at the cylinder where the key goes:
If your cylinder fails the stamp test or the protrusion test, it belongs on this month's to-do list rather than next year's.
Here is the part most guides skip. Cylinders come in sizes, measured in millimetres from the central fixing hole out to each end, and doors vary. Fit a cylinder that is 5mm too long for the door and it protrudes — handing back the very grip the anti-snap design exists to deny. We are called to doors where someone has paid for a genuinely excellent three-star cylinder and lost much of its benefit to the wrong size bought off a shelf.
A proper fit means measuring the door with the handle furniture on, choosing the exact size (cylinders are sized in 5mm steps, and offset sizes exist for a reason), and checking the finished protrusion with the door closed. It takes a locksmith minutes; it is the difference between owning the rating and merely owning the receipt.
A named, vetted master locksmith covers your area — no call-out fee.
A quality three-star or Diamond cylinder, supplied and fitted, typically lands in the region of a takeaway-for-four per door — and it is a one-off cost that lasts for years. Compare that with the average cost and disruption of a burglary, and with the fact that some insurers now ask about cylinder ratings on uPVC doors, and the equation settles itself. Prioritise the doors burglars prefer: the back door, the side door, the door hidden from the street. The front door matters too, but the unseen doors are where snapping happens.
One honest caveat: anti-snap cylinders defend against snapping, not against an unlocked door. A three-star cylinder in a door that is never properly locked — handle lifted, key turned — protects nothing. Hardware and habits work together.
Keys inside, keys lost, key snapped, or a handle that won't lift — four different problems with four different answers. A locksmith's guide to handling each one, and the first-ten-minutes mistakes that turn cheap jobs expensive.
Your insurance policy says BS3621 — but if your doors are uPVC or composite, that's not even the right standard to look for. Which standard fits which door, how to read the Kitemark, and the sixty-second audit for every door in the house.
Built from what actually fails on British homes — not a camera sales pitch. A timed walk-round covering cylinders, deadlocking habits, letterboxes, windows and the side gate, with a score at the end and fixes ordered by cost.