⚙️ How They Work
Push the lever or pin down - two thick metal "teeth" bite onto the aluminium track or frame. The door is blocked both horizontally and vertically (against lifting).
Add-on Locks for Sliding Aluminium Windows: Are they worth it and which to choose?
If you live in a home built in the '90s or '00s, there is a huge chance your lounge features the classic overlapping sliding aluminium doors. They saved space and were fashionable - but they were also the burglar's delight.
The factory "lock" is usually a thin plastic hook. The burglar inserts a pry bar at the bottom, lifts the sash off the track and the entire door comes out silently. If a full replacement isn't in the budget, the market offers add-on (aftermarket) locks.
1. Clamp Locks / Engagement Mechanisms (Cal Type)
The most famous "hack" in the Greek market. These are small, solid metal devices that are screwed externally onto the aluminium profile (usually at the bottom or middle of the door).
✅ Advantages
Installed easily with 2–4 screws by anyone, even as DIY. Cost: €10–25. They completely immobilise the sash, blocking both sliding and lifting.
❌ Disadvantages
They are visible (aesthetically modest) and require manual locking every time you go out to the balcony - which becomes tedious in daily life.
2. Double-Security Pins (Overlapping Sash Locks)
Ideal for overlapping windows where the right and left sashes overlap in the middle.
📌 How They Work
The installer drills a hole through both profiles at the overlap point. A thick steel pin (often key-operated) is inserted. When pushed in, the two sashes become "one body".
✅ Advantages
Extremely discreet mechanisms. The burglar cannot slide or lift the sashes. No visible external changes to the window.
⚠️ Caution
Installation requires precision - if drilled incorrectly, you may hit the glass. Have it done by an experienced fabricator.
💰 Cost & Availability
Double-security pins are readily available at hardware stores and aluminium fabricators. Cost ranges from €15 to €40 per point, plus installation labour. Fit at least two pins (high and low on the overlap) for comprehensive coverage.
3. Replacing the Main Mortise Lock
Instead of adding external bolts, you can replace the old, weak mortise lock with a modern multi-point hook lock.
🔧 How It Works
Externally it looks like the old lock (same handle), but internally it has 2, 3 or 4 steel hooks that "embrace" the frame. A dramatic security upgrade with zero external change.
✅ Advantages
The cleanest and most aesthetically flawless solution. Nothing is added externally. Security increases dramatically without visible alterations.
⚠️ Requires a Professional
A specialised aluminium fabricator is needed for installation because the new lock must match the exact dimensions of the old profile. Installation labour starts at around €60 per sash.
📏 Profile Compatibility
Before purchasing a hook lock, the technician measures the "backset" dimension (centre-to-edge distance of the cylinder). Most Greek aluminium profiles have a 25 or 30 mm backset - a compatible lock is almost always available.
4. Are They Actually Worth It?
A €15 clamp lock will not transform a 1995 aluminium door into an RC3 vault. If the burglar has ample time and heavy tools, he will get in. However, the burglar's greatest enemy is time.
🛡️ Deterrence
The burglar shines his torch and sees the external clamps. He knows the job just became 3 times more time-consuming. Often, he simply chooses not to bother.
⏱️ Delay
They neutralise the "silent" lifting trick. The burglar is forced into violence and noise - exactly what he avoids.
💶 The Value
The best low-budget move to fortify old windows - until the time comes for a full upgrade.
💡 Tip: Combine clamps at the base, a pin in the middle and a handle lock at the top - three locking points = triple the time for the burglar.
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Mushroom Cams vs Plain Rollers: How They Stop Burglars Burglary Resistance Classes (RC1 to RC6) Lift & Slide Windows: How the Mechanism Works Multi-Point Locking Mechanism: Ultimate Window Security
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