Next put a new latch in and replace the door knob.
How to install door lock.
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If you re installing a lockset in an existing door take out the old lockset and measure the backset the distance from the door edge to the center of the lockset hole.
If you re in a situation where you cannot or do not want to use a drill to install your lock there are a couple ways of installing an interior door lock without a drill.
To change the lock on a regular door knob first use a screwdriver to remove the door knob and the old latch.
Once you have the kit remove the lock cylinder from the door knob so you can change the pins inside.
If your new deadbolt has a concealed screw for the interior door knob consult the installation instructions for your specific lock.
The measurement is usually 2 3 8 inches for interior doors and 2 3 4 inches for exterior doors.
For added security take the time to learn how to install a deadbolt lock on every exterior door.
Alternatively you can buy a re keying kit for the lock you already have.