Changing interior door knob locks that have no visible screws is not as difficult as you may think. All door knobs use two screws to secure the inner and outer assembly to each other. Most door knobs have these screws visible on the outside of the decorative plate. Screws that are not visible are actually hidden behind the plate. The inside door knob handle secures using a pin. To access the hidden screws requires removal of the inner door knob handle and decorative plate.
Things You'll Need
Large paper clip
Small flat-head screwdriver
Replacement door knob lock
Remove Door Knob Assembly
Open the door so both sides are accessible. Look under the inside door knob for a small slot or hole. The notch or hole is on the neck between the knob and the decorative plate.
Straighten out a large paper clip and insert it into the hole until you feel resistance. The resistance is the spring-loaded pin securing the handle to the assembly. Insert a small flat-head screwdriver into the notch, if your door knob has a notch instead of a hole.
Press inward on the retaining pin with the paper clip or screwdriver. Pull the inside knob away from the door while pressing on the pin. Remove the paper clip or screwdriver when the knob begins to pull away. Pull the knob completely off.
Look for a small notch between the back of the decorative plate and the door. Insert the flat-head screwdriver there and pry the plate away from the door. Some decorative plates will not have a notch. Grasp the plate with your fingers and turn it counterclockwise to release the plate. Removing the plate reveals the two screws securing the door knob assembly.
Remove the two screws with a Phillips-head screwdriver. Hold the outer knob and pull the inside knob stem out. Pull the outer door knob away.
Turn the two screws that secure the latch assembly counterclockwise with the Phillips-head screwdriver. Pull the latch assembly out. Remove the two screws securing the strike plate to the door jamb with the Phillips-head screwdriver. Lift the strike plate away.
Install Door Knob Assembly
Set the new latch assembly into the edge of the door and secure it with the retaining screws. Insert the outer knob into the door. This knob has two threaded sleeves and a flat metal piece that will fit into the latch assembly.
Hold the outer knob to the door and position the inside knob handle stem and retaining plate into the door. Wiggle and adjust the inside knob stem until it fits over the outer knob sleeves. The flat metal piece will also fit inside a slot on the inside knob stem. Both door knobs should fit flush against the door.
Thread the two screws through the retaining plate and into the threaded sleeves of the outer knob. Tighten with a Phillips-head screwdriver. Slide the inner decorative plate over the stem and either snap it over the retaining plate or turn it clockwise to secure it.
Slide the inner handle over the stem until the lock pin engages. Place the new strike plate onto the jamb and secure with the screws.
Replacement interior door knob locks are available at home improvement centers.