Anti-snap locks and BS 3621, explained plainly
What lock snapping is, what 'anti-snap' actually means, and how TS007, Sold Secure and BS 3621 relate to your home insurance.
Lock snapping is the reason "anti-snap" is a phrase homeowners now have to know. It's the most common way uPVC and composite doors get forced in the UK, it needs almost no skill, and the defence against it costs about the same as a takeaway. Here's the whole thing in plain terms.
The gist
Lock snapping breaks the euro cylinder on a uPVC door to open it. A basic cylinder gives way in seconds. An anti-snap cylinder is built with sacrificial sections, so it breaks in a controlled way and the working part stays protected. Look for TS007 3-star or Sold Secure Diamond markings. Separately, BS 3621 is the standard for mortice deadlocks on wooden doors, and your home insurance may require it.
How lock snapping works
On most uPVC and composite doors, the euro cylinder pokes out slightly past the handle — sometimes a few millimetres, sometimes more if it was badly sized. An attacker:
- Grips that protruding section with mole grips or a purpose-made tool.
- Snaps it off. Brass and cheap alloys shear easily.
- Works the exposed cam in the middle to retract the bolts and open the door.
No noise to speak of, no lock-picking skill, under a minute. The police-backed Secured by Design scheme has flagged it for years, which is why building standards and insurers moved on it.
What anti-snap actually means
An anti-snap cylinder is engineered to fail safely. It has deliberate break lines near the outer end, so when force is applied the front section snaps away as designed — and behind it sits a hardened core that still holds the door locked. The attacker is left with a broken stub and a door that won't open.
Good cylinders often combine several defences:
- Anti-snap — the sacrificial break design above.
- Anti-drill — hardened pins or plates that chew up drill bits.
- Anti-pick and anti-bump — extra pin designs that defeat manipulation.
A cylinder marketed as "3 star" generally has to resist all of these on its own.
TS007, Sold Secure and the star ratings
Two schemes matter, and they overlap:
- TS007 (the Kitemark star rating). A cylinder can be 1 star or, on its own, 3 star. A 1-star cylinder plus 2-star "security hardware" — a proper anti-snap handle or escutcheon — also gets you to a 3-star combination. What you want on an exposed door is 3 stars total, however it's made up.
- Sold Secure (run by the Master Locksmiths Association). Its Diamond grade for cylinders is the equivalent benchmark. Sold Secure publishes the list of approved products.
If your key or cylinder has no star marking and the door's more than a few years old, treat it as a basic cylinder.
BS 3621 and your insurance
BS 3621 is a different thing, mostly for wooden doors. It's the British Standard for a lock — usually a 5-lever mortice deadlock — that resists drilling, picking and forcing for a set time, marked with a kitemark and "BS 3621".
Why it matters: a lot of home insurance policies specify that final exit doors must have a BS 3621 lock. If yours does and you don't, a burglary claim can be reduced or refused. The fix is to read the "security" or "minimum security requirements" part of your policy and fit locks that match it. Which? has a plain-English rundown of the lock types if you want to check what you've got.
Do you need to upgrade?
Quick self-check:
- uPVC or composite front door with a plain, unmarked cylinder? Upgrade to a 3-star anti-snap cylinder. This is the highest-value change you can make, and it fits the same hole.
- Cylinder sticking out more than about 3mm past the handle? That overhang is what gets gripped. Get it re-sized as well as upgraded.
- Wooden exit door with only a night latch? Add a BS 3621 mortice deadlock, especially if your policy asks for one.
- Just had a break-in or an attempt nearby? Do it now — see what to do after a break-in.
None of this is a big job. An anti-snap cylinder or BS 3621 lock goes in during a normal visit, and the doors are tested before we leave. If you're in Bedfordshire and not sure what you've got, call 07362 773424 and we'll take a look.
Frequently asked
- What is lock snapping?
- A forced-entry method for uPVC and composite doors. The attacker grips the part of the euro cylinder that sticks out past the handle, snaps it off, and then manipulates the exposed centre to open the door. On a cheap cylinder it takes seconds and little skill.
- How do I know if my cylinder is anti-snap?
- Anti-snap cylinders have deliberate weak points so they break in a controlled way, leaving the working part protected. Look for a '3 star' or 'TS007 3-star' marking on the key or cylinder, or a Sold Secure Diamond mark. If yours has no markings and the house is more than a few years old, assume it isn't anti-snap.
- What does BS 3621 mean on a lock?
- It's the British Standard for a lock that resists drilling, picking and forcing, shown with a kitemark and the number. It usually applies to 5-lever mortice deadlocks on wooden doors. Many home insurance policies require BS 3621 locks on final exit doors.
- Will my insurance be void without the right locks?
- It can be. If your policy specifies a lock standard for exit doors and you don't have it, an insurer can reduce or refuse a burglary claim. It's worth reading the 'security' section of your policy and fitting locks to match.
- Is upgrading to anti-snap locks expensive?
- No — it's one of the cheapest security improvements you can make. An anti-snap euro cylinder costs a little more than a basic one and fits in the same space. On an exposed front door it's the single upgrade most worth doing.
- Do anti-snap cylinders need special keys?
- No. They use standard keys and fit the standard euro-cylinder cut-out. From the outside, most people wouldn't know the difference — which is rather the point.
Locked out, or a lock playing up?
Call Gabriel direct. Send a photo of the lock and you will get the likely price on the phone before anyone drives out. No call centre, any hour.