When you remove the faceplate it will reveal the inside of your knobset lock.
How to remove security door lock.
Unscrew this plate and remove the latch from the door if possible.
This is a video on how to remove the euro cylinder lock from a door.
Once this is removed a locksmith can re key this for you.
Cylinder locks are extremely common but how to remove the cylinder is not quite as obvious as a knob door lock.
One way screw is a special screw that common use for secure doors or windows.
There should be a series of screws that connect that portion of the lock to your door.
Remove this screw using a drill or screwdriver.
Once it goes in that is it.
Grasp the interior trim in one hand and the exterior trim.
Step 2 look for a small set screw at the base of the handle.
Security gate cylinder removal.
Once you remove the screws the lock should become loose and you can pull both sides of the lock out of the door.
Remove the screws in the knob with a screwdriver.
Removing a cylinder door lock.
Removing the cylinder from a door lock is a simple way of keeping the lock handle that you have while changing the cylinder lock inside of it.