"Chris Hogg" wrote in message
...
On Wed, 6 Mar 2019 19:39:21 +0000, Rob Morley
wrote:

On Wed, 06 Mar 2019 18:46:07 +0000
(Alan J. Wylie) wrote:

I found this sliding patio door lock fitted on the house I've just
bought.

https://rfvt.org.uk/tmp/apprentice.jpg

I wonder if it would otherwise be possible to lift the door out of its
track (and off a normally positioned bolt).

My thought too. Useless as a conventional lock, but it might prevent a
burglar levering the sliding door up off its track, a not uncommon
method of forced entry with earlier patio doors, I believe.

Doesn't work with mine which are from the very early 1970s.
The standard lock has a great big 12mm roughly pin that is
fixed into the fixed frame which goes into a hole in the moving
part of the door and is gripped by the lock when its locked.
That stops you lifting the door when its locked.

I assume
there's a conventional lock as well.