I seem to remember that there is a tiny screw in a hole underneath which has to be screwed in so that the barrel of the lock mechanism can slide out of the metal support. It only becomes obvious when you have done it. Obviously it has to be a bit obscure to put off thieves. It was two years ago that I did mine, and I can't remember exactly what I did, but it took me some time to find it. EdwinAni advice on how to this please