Ongoing Puzzlement Over Window Locks

Every couple of weeks we get a call concerning the improving of window locking where no improvement is possible (save fitting bars).

Sliding sash windows

In many previous posts I have pointed out the hopeless nature of sliding sash windows. In terms of locking, frequently they can be improved. An acorn catch is useless and there’s an easy way to open them from the outside.

Acorn Catch

The Brighton catch and the Fitch are better. They are also  available in locking versions that are quite effective.


But with any of those central mechanical catches it is usually worth adding sash stops (or sash bolts if you live in an area – unlike London – where there’s little house movement).

Casement windows

These are windows (typically wooden) that are hinged on one side. They are usually secured with a stay (the arm that keeps the window open to one of several angles) and a catch. Unless they are hopelessly undersized, there is usually no way to bypass the stay or the catch from outside if they are in the fully closed position. (Some catches have a ventilation position that can be opened from the outside.)

Normally the only way through a properly shut casement window is to break the glass. And if a burglar is prepared to break the glass well they’re coming in whatever you do. Which is why accessible windows should be lit and clearly visible from the street.

Espagnolette windows

These will typically be newer and made of PVC. A handle operates a couple of bolts that lock the window into the frame. There will be a click as you operate the bolts and the handle gets to the locked position; then you have to press a button in before you can move the handle to the open position. The bolts are very difficult to bypass anyway, but even if the window is loose in the frame, if you’ve heard that click and the handle cannot be moved back to the open position without pressing in the little button in the handle then the window is secure; the only way in is to break the glass.

Sometimes there is a key with an “espag” handle. But this is not to increasy the security against someone coming through unwanted from the outside, this is to prevent someone already inside from¬† opening and leaving via the window.

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