Pencarrow
Western Thunderer
One of the doors (that which closes first) would have a bolt top and bottom, I believe. The one which closes against it will have only one bolt and this is used to hold the door open.
The lock then holds the door with one bolt shut.
Brian
I've been looking at doors in close-up photos in the Southern Nouveau book and there's no sign of a bolt at the top of the door that opens first. I presume it is on the second opening door instead.
A typical example below from pg338 dated 24-04-51.
I'll be adding second bolts to the tops of the other doors though.