Cylinder Protrusion | The Fitting Fault Burglars Love

Most break-ins through uPVC doors in DN10 don't happen because someone picked the lock. They happen because the cylinder is sticking out far enough to grip, and nobody ever noticed.

That's not a lock quality problem. It's a fitting problem. And it's one I see constantly, on new doors as well as old ones.

Why protrusion is the real vulnerability

When a euro cylinder sits proud of the door furniture by more than 3mm or so, an attacker can get a grip on it with mole grips or a large adjustable spanner, apply sideways leverage, and snap the barrel. The whole thing takes under ten seconds. No skill, no specialist tools, no patience required.

The snap itself breaks the cylinder at its weakest point. If the cylinder has a sacrificial snap zone, as a TS007 3-star rated cylinder should, the idea is that the outer section breaks away harmlessly before the inner cam is exposed. But here's what the marketing doesn't always tell you: even a cylinder with a snap zone can fail that test if there's enough protrusion for an attacker to get a proper mechanical advantage. The snap zone buys you time and uncertainty. Excessive protrusion gives it straight back.

I had a job in Harworth last spring. Composite door, less than two years old, fitted by a local trader. The homeowner had paid for a decent cylinder, not a bottom-shelf product. But the cylinder was sitting 9mm proud of the escutcheon because the furniture was the wrong size for the door thickness. Nine millimetres. That's more than enough to grip. The cylinder was the least of the problem.

What 'flush fitting' actually means

The cylinder face should sit either flush with the outer face of the door furniture, or slightly recessed behind it. Some locksmiths will tell you up to 3mm protrusion is acceptable. I'd rather see it at zero.

Door furniture, meaning the handle and escutcheon plate that the cylinder sits inside, comes in different depths to suit different door thicknesses. Standard uPVC and composite doors are typically 70mm overall, though many modern composite doors run to 74mm or even 80mm. If the furniture is cut for a 70mm door and the door is 74mm, the cylinder ends up sticking out. That's not a cylinder fault. It's the wrong furniture for the job.

The fix is usually straightforward. Sometimes it's just a case of fitting a longer cylinder to suit the door. More often it means fitting correctly sized furniture at the same time. Total parts cost on most jobs runs between £40 and £90 depending on specification. Not expensive for what it solves.

The cylinder still matters, but not for the reason most people think

People shopping for security upgrades tend to focus on anti-pick performance, because that's what the packaging talks about and what the YouTube test videos demonstrate. Fair enough, those videos are impressive.

But anti-pick is not where most attacks happen. Snap attacks account for the large majority of cylinder-based forced entries across UK forces, though exact percentages vary considerably by area and time period. South Yorkshire and Nottinghamshire have both seen significant numbers of snap-related burglaries in recent years. The point is: pick attacks require skill, leave no trace, and tend to appear in targeted or commercial contexts. A semi-detached in Austerfield or Tickhill is far more likely to face a snap attempt than a lock-picking one.

So when choosing a cylinder, what actually matters is the snap zone and the overall construction. A TS007 3-star rated cylinder, whether that's an Ultion, an Avocet ABS, or similar, has passed independent testing for anti-snap, anti-drill, anti-pick, and anti-bump performance. That rating is meaningful.

If you're considering ERA Fortress, it also carries TS007 3-star, but I'd be straight with you: its track record for snap resistance under heavy lateral force is not quite at the level of the Ultion or Avocet ABS in my experience. It's not a bad product, but if snap protection is the priority, which it should be, I'd lean toward Ultion or Avocet ABS first.

One more thing worth understanding: SS312 Diamond is a Secured by Design approval that goes beyond the TS007 3-star rating itself. It also requires the cylinder to meet specific physical installation criteria, including protrusion limits and compatible door furniture. So you can fit a TS007 3-star cylinder and still not meet SS312 Diamond if the installation isn't right. The standard is about the fitted door system, not just the cylinder in the packet.

The things people upgrade instead

I'm not having a go at anyone who's spent money on locks. But I do think the trade, including some of my competitors, does a poor job of explaining what matters in what order.

Here's what I see people buy when they want to improve security:

• Anti-pick cylinders, fitted with the same protrusion problem as before
• Smart locks added to a door that's still using the original worn multipoint mechanism
• High-spec cylinders in doors where the keep is held by 25mm screws into a hollow frame

All of those miss the point. The cylinder protrusion issue comes first because it's the primary attack method. Then the keep and frame reinforcement, because a kick to a weak frame bypasses every lock ever made. Then the multipoint mechanism itself, brands like GU, Fuhr, Maco, Roto, and Winkhaus all make decent gear, but a worn mechanism that's only catching on one hook is a liability. Anti-pick performance is a genuine bonus on top of that, not the foundation.

I've refitted cylinders on Martin Common, out towards Rossington, and in Finningley where the original fitter had simply never thought about protrusion. On one job in Misson the cylinder was sticking out so far the homeowner could see it without bending down. They'd lived with it for three years.

The obvious objection

Someone will say: if I fit an anti-snap cylinder flush, but a skilled attacker has a bump key, am I still at risk?

Technically, yes, a non-pick-resistant cylinder is still bumpable. But TS007 3-star cylinders cover anti-bump as part of the rating. So a properly fitted, properly specified cylinder addresses both. The argument isn't snap versus pick. It's that fixing the fitting problem first, then choosing a rated cylinder, gets you the most protection for the least spend.

The honest caveat

If you're running commercial premises, managing multiple tenancies across DN10 or out towards Retford and Blyth, or you've had a specific threat assessed, then key control becomes a genuine priority alongside all of the above. Mul-T-Lock MT5+ and similar high-security systems offer restricted key cutting that standard TS007 cylinders don't. That's a real benefit for landlords. It's just not where most domestic homeowners should start.

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If you're not sure how far your cylinder protrudes, take a look now. Hold a flat card against the door furniture and see whether the cylinder sits behind it or in front of it. If it's in front, that's worth sorting.

Rapid Response covers Bawtry and across the DN postcodes. We aim to reach most call-outs within 30 minutes. Pricing is confirmed on the call before anyone comes out, and there's no pressure if you'd rather think about it first.