On Sun, 23 Mar 2014 22:26:36 +0000, dennis@home wrote:

If you are trying to stop them lifting the door out of its track and/or
sliding then you can fit locks that the bolt goes into a hole in the
door and the lock is screwed down through the aluminium into the sub
frame.

If I understand you correctly, you're suggesting putting the lock
sideways on the external frame so that the lock's bolt pokes horizontally
into the door? Unfortunately, the shape of the external frame doesn't
really lend itself to that in my case:

http://i.imgur.com/6daIdSo.jpg