The best french door security will have a 3 point locking system.
Securing wooden french doors.
Traditional wood french doors have many small panes of glass.
Even if these are tight enough to prevent the fixed door from.
Because french doors have no center frame or support they are very weak in the center.
Three point locking mechanisms are best for french doors.
Add one side half deadbolts to the top and bottom of each door.
The fixed door on many french doors is held closed by a pair of barrel bolts that sink into the top jamb and threshold of the doorway.
When french doors open outward the hinges are exposed on the outside.
This alone will make it a lot more difficult for a burglar to force the doors open.
For doors with a bolt that slides to lock along the top and bottom of the door you can permanently lock the door by drilling a hole into.
However a deadbolt that locks both doors together and single sided deadbolts in the top and bottom of both doors are a good combination for securing both doors.
Install a commercial grade double sided deadbolt into the active side of the door or alternatively install a double side high security deadbolt into the active side of the french door.
French doors are difficult to secure for several reasons involving the following weak spots.
For doors that come as a pair consider locking securing one of them permanently.