Thinking about changing your own door lock?

Maybe the key’s stopped working, the door won’t lock, or you’ve just moved into a new place and want peace of mind.

Whatever the reason, this guide shows you what’s going on inside a typical uPVC door and helps you understand whether it’s something you can fix yourself — or if it’s time to give Locksmith Kev a ring.

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🔍 What’s Inside Your uPVC Door Lock?

Most modern uPVC doors use a multi-point locking mechanism. That’s a long strip of hooks and bolts running inside the edge of the door. But the real action happens in the middle, where you’ll find:

• The Euro Cylinder – this is where the key goes

• The Gearbox – this operates the locking hooks

• The Retaining Screw – holds the lock in place

• The Handle Spindle – connects both handles

📸 See our labelled photo below for a full breakdown ⬇️

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🔩 Why Your Key Might Turn but the Door Won’t Open

This is one of the most common issues I’m called out to fix.

In most cases:

• The cylinder is fine

• The gearbox inside has failed — often from wear and tear, or slamming the handle

You can swap the cylinder easily, but if the gearbox has gone? That’s a tougher job, and forcing it can cause more damage.

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🛠️ How to Replace a Euro Cylinder Lock (Basic DIY)

If it’s just the cylinder and everything else works, here’s how you can replace it yourself:

1. Open the door fully

2. Remove the retaining screw (it’s at the side of the door, in line with the cylinder)

3. Turn the key slightly while gently sliding the lock out

4. Slide in your new cylinder

5. Reinsert the screw and test the lock

❗ Make sure the new lock is the correct length — flush with handles, not sticking out.

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🚨 When Not to DIY

You should call a locksmith if:

• The key turns but nothing happens

• You’ve removed the cylinder and the door still won’t open

• The handle feels floppy or the hooks won’t engage

• You’re not sure which part is faulty

These are all signs the gearbox has failed, and we carry replacements on the van — fitted same day, no damage.

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📞 One Call. One Solution.

If you’ve started a job and got stuck — no worries.

Locksmith Kev is local, DBS checked, and fully stocked to sort any door issue across Newcastle, Cramlington, Gosforth, Blyth and surrounding areas.

✅ Euro cylinders

✅ Gearboxes

✅ Handles & full strip repairs

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🔗 Need More Help?

📚 Browse more help-yourself guides here:

👉 https://locksmithkev.co.uk/5-minute-reads

📸 Follow us on Facebook for live job updates, tips & repairs:

👉 facebook.com/locksmithkev