How do I know which multipoint mechanism my uPVC door has?

You can identify your mechanism by measuring three things: the PZ distance (spindle hole centre to keyhole centre), the backset (faceplate edge to keyhole centre), and the overall length. The brand name is usually stamped on the metal faceplate visible on the door edge. Common brands include Mila, GU, Yale, Fuhr, and Winkhaus. If you are unsure, send me a photo of the faceplate on 07735 336175 and I can usually identify it.

How long does a uPVC door lock mechanism last?

A typical multipoint locking mechanism lasts 10 to 15 years with normal use. With proper maintenance — regular lubrication, not slamming the door, keeping a light key ring — you can extend this to 15 to 20 years. The gearbox is usually the first component to fail. Most Coventry homes built in the late 1990s and 2000s are now reaching the point where mechanism replacement is needed.

Can I replace a uPVC door lock mechanism myself?

It is technically possible but not recommended for most people. You need to match the exact mechanism specifications (PZ distance, backset, overall length, locking point positions), which can be tricky. Getting it wrong means the door will not lock properly. A professional locksmith can identify, source, and fit the correct mechanism in about an hour, typically costing between £89 and £200 depending on the brand.

What is the difference between hooks and rollers on a uPVC door?

Hooks are security-focused locking points that swing out and hook into frame keeps, providing strong resistance to forced entry. Rollers (compression bolts) push out and compress the door against the frame seals, primarily keeping drafts and rain out. A good multipoint mechanism uses both: hooks for security at top and bottom, and rollers for compression and weatherproofing in between.

uPVC Door Lock Mechanisms Explained: Gearboxes, Hooks, and Rollers

Inside every uPVC door is a multipoint locking mechanism with gearboxes, hooks, rollers, and deadbolts. Here is how it all works — and what fails first.

What Is Inside Your uPVC Door?

If you have a uPVC door — and if you live in Coventry, there is a very good chance you do — then behind that handle and cylinder sits a multipoint locking mechanism. It is the single most important security component in your door, and most people have never seen one.

I have been replacing these mechanisms across Coventry for years, from the 1990s-era estates in Canley and Tile Hill to the newer builds around Walsgrave and Binley. In this post, I will explain exactly how your uPVC door lock works, what each component does, and what to look out for when things start to fail.

The Multipoint Locking Mechanism: An Overview

A multipoint locking mechanism is a long, flat metal strip that runs vertically inside the edge of your uPVC door. When you lift the handle and turn the key, it engages multiple locking points simultaneously — typically three, five, or even seven points along the length of the door.

This is fundamentally different from a traditional wooden door with a single Yale nightlatch or mortice deadlock. A multipoint system spreads the locking force across the full height of the door, making it far harder to force open.

The Key Components

The Gearbox

The gearbox is the central unit of the entire mechanism. It sits in the middle of the door, directly behind the handle and the euro cylinder. Think of it as the brain of the operation.

The gearbox houses the keyway (where the cylinder sits), the handle spindle connection, and the internal gears that translate your handle lift and key turn into mechanical movement up and down the door.

When you lift the handle, the gearbox pushes rods upward and downward simultaneously. When you turn the key, it engages the deadbolt within the gearbox itself.

The gearbox is also the component that fails most often. After 10 to 15 years of daily use — and that covers a huge number of Coventry homes built in the late 1990s and 2000s — the internal gears start to strip. You will notice the handle feeling sloppy, or the key not turning smoothly. That is the gearbox telling you it is on the way out.

Hooks

Hooks are locking points that sit at the top and bottom of the mechanism. When you lift the handle, they swing out from the edge of the door and hook into metal keeps (strike plates) fitted in the door frame.

Hooks provide serious resistance to forced entry. They are particularly effective against kick-in attacks because even if the door flexes under impact, the hooks remain engaged in the frame keeps. A door with two or more hooks is significantly harder to force than one relying on rollers alone.

Rollers (Compression Bolts)

Rollers are mushroom-shaped or cylindrical bolts that push out from the door edge and compress into matching keeps in the frame. Their primary job is to pull the door tight against the frame seals, keeping drafts and rain out.

Rollers provide moderate security but their main function is compression and weatherproofing. On a well-maintained door, the rollers keep the seal tight so you do not get draughts whistling through in winter — a common complaint I hear on jobs across Coventry.

The Deadbolt

The deadbolt sits within the gearbox and is the final locking action. After you lift the handle (which engages hooks and rollers), turning the key throws the deadbolt into the frame keep.

The deadbolt is what makes the door properly locked rather than just latched. If you only lift the handle and walk away without turning the key, the deadbolt is not engaged — and your door is significantly less secure. I cannot stress this enough: always turn the key.

How It All Works Together

Here is the sequence of what happens when you lock your uPVC door:

**You close the door** — the latch (a spring-loaded bolt on the gearbox) clicks into the frame, holding the door shut but not locked.

**You lift the handle** — this activates the gearbox, which pushes the hooks out at the top and bottom, and extends the rollers into their frame keeps. The door is now compressed tightly against the seals.

**You turn the key** — this rotates the euro cylinder, which in turn throws the deadbolt within the gearbox. The door is now fully locked at all points.

To unlock, you reverse the process: key turn retracts the deadbolt, pressing the handle down retracts the hooks and rollers, and you can open the door.

Common Brands and How to Identify Yours

Not all multipoint mechanisms are the same. There are several major manufacturers, and they are not universally interchangeable. The most common brands I encounter on jobs in Coventry are:

**Mila** — very common in UK-manufactured uPVC doors from the 2000s onward

**GU (Gretsch-Unitas)** — German-made, found in higher-specification doors

**Yale** — widely available and often fitted as replacements

**Fuhr** — another German manufacturer, common in commercial and higher-end residential doors

**Lockmaster** — a universal replacement brand that covers many common sizes

**Winkhaus** — premium German mechanisms, excellent quality

How to Identify Your Mechanism

If you need a replacement, you will need three measurements:

**PZ distance** — this is the distance from the centre of the handle spindle hole to the centre of the keyhole (euro cylinder). Common PZ distances are 70mm and 92mm. This is the most critical measurement.

**Backset** — the distance from the front edge of the mechanism (the faceplate) to the centre of the keyhole. Common backsets are 35mm and 45mm.

**Overall length** — the total length of the mechanism from top to bottom. This varies significantly between brands and door sizes.

You will also need to note the shape of the faceplate (flat, rounded, or U-shaped) and the positions of the locking points.

If this sounds complicated, that is because it can be. I carry a range of common mechanisms in my van and can identify yours on site. Give me a call on 07735 336175 and I can usually tell you the brand from a photo of the faceplate markings.

What Fails First

In my experience, the order of failure is almost always:

**Gearbox** — stripped teeth or worn internal components after 10 to 15 years. Symptoms include a sloppy handle, difficulty turning the key, or the handle not springing back up.

**Hook springs** — the springs that retract the hooks can weaken or snap, leaving hooks stuck in the extended or retracted position.

**Rollers** — these can seize up or lose their compression, leading to draughty doors.

**Deadbolt** — less common but can jam if the gearbox internals are failing.

The gearbox is the weak point because it has the most moving parts and bears the most mechanical stress. If your door is from the late 1990s or early 2000s and you have never had the mechanism replaced, it is likely approaching end of life.

When to Call a Locksmith

If your uPVC door is showing any of these symptoms, it is time to get it looked at:

The handle feels loose or does not spring back after lifting

You have to lift the door by the handle to get it to lock

The key is increasingly stiff to turn

You can hear grinding or clicking when operating the handle

The door does not seal properly against the frame

Do not wait until the mechanism fails completely — you could end up locked out, or worse, locked in. A mechanism replacement typically costs between £89 and £200 depending on the brand, and I can usually complete the job within an hour. Call me on 07735 336175 or check our [prices page](/prices) for current rates.

For more on whether your lock needs replacing or just repairing, see our guide on [how to tell if your uPVC door lock needs replacing](/blog/upvc-door-lock-needs-replacing). And if you are thinking about upgrading your cylinder at the same time, take a look at our [best euro cylinder upgrades for 2026](/blog/best-euro-cylinder-upgrades-2026).

If you are in the Coventry area and need a uPVC door mechanism replaced, I cover all local areas including Tile Hill, Canley, Earlsdon, Coundon, Binley, Walsgrave, and beyond. See our full [areas covered](/areas/) page for details, or visit our [uPVC lock repair service page](/services/upvc-lock-repair) for more information.