Double door insight: Master and Slave
Double doors always have a ‘master’ door and a ‘slave’ door. The master is the main/active door and the slave is the door that is passive/often fixed in place.
A flush bolt is often used on the slave door which enables this door to be closed and held in place and also to hold both doors in the frame when they are closed together. Flush bolts are usually situated on the edge at the top of the door (see image). There is the option to have a flush bolt on the bottom edge of the door as well, although it is important to note this will need a hole/mechanism in the floor to operate.
Double doors can have a latch or a roller ball catch to operate them, this is up to the client and can depend on how often the doors will be open/closed.
If a latch is used this will be fitted on the master door and will need a handle to operate the latch. It can look odd to have one door with a handle and one door without so we would usually install a dummy handle on the slave door. This dummy handle would be fitted to a tailor dummy spindle and would not actually move or operate anything, it is purely for aesthetics.