Secure the Active Leaf
Use a drill or screwdriver to remove the screws holding the existing lock in place. Many French doors come with fairly weak deadbolt locks. If yours has a bolt that is shorter than 1 inch, replace it with a more secure lock.
Purchase a new deadbolt made of solid steel for the highest level of security. If your deadbolt will be located at least 6 inches from any glass panels, a single deadbolt will be sufficient. If not, purchase a double deadbolt.
Install the new deadbolt into the existing hole in your door. It may be necessary to router or chisel the hole to make it large enough for the new lock. Secure the lock into place using the supplied screws.
Test the lock. Shut the door and use your key or the thumb turn to throw the deadbolt. If it fits securely into the existing strike, you can leave the strike as it is. If not, remove the existing strike and install the one that came with your new lock. Again, it may be necessary to chisel out the hole slightly to accommodate the new deadbolt.
Retest the lock to ensure it is functioning properly. If you've purchased a double deadbolt, you'll need to leave the inside key somewhere near the lock to allow for safe exit during an emergency. Do not leave the key in the lock, as this makes it too easy for burglars to enter the home. Make sure all family members know where the key is located.
Secure the Inactive Leaf
Purchase a pair of solid steel bolts with a 1-inch throw to secure both the top and bottom of the door.
Surface-mount the bottom bolt. Screw it to the face of the door so the bottom of the lock body is flush with the bottom of the door. Throw the bolt so that it hits the floor, then trace around it with a pencil.
Use a drill or router to create a hole in the floor to accommodate the bolt. Test to see if the bolt fits in the hole before covering the hole with the strike plate.
Surface-mount the top bolt. You'll need a unit with a surface-mounted strike to accept the bolt. Screw the bolt casing to the face of the door so it is flush with the top of the door. Align the strike on the frame so it fits tightly to the bolt casing. Screw the strike in place, then test the bolt to ensure it is operational.
Things You Will Need
- Single or double deadbolt lock
- Rackbolts (flushbolts)
- Tape measure
- Consider mortising bolts into the door and frame for added security. Choose a unit designed for mortising, then use your router or chisel to create appropriate holes in the top and bottom of the door. Slide the bolt into these holes and screw the cover plates in place. Drill or router holes in the floor and the top of the door frame to accept the bolts, then cover these holes with the strike plates. Test that the bolts are operational before proceeding.
- In some areas, double deadbolt locks are banned by local fire safety codes. If this is true in your area, consider adding flush bolts to the active leaf to keep the door secure when you're away from the home.