Pull the top drawer of the cabinet out until it is fully extended. Lift the front end of the drawer until it is released from the cradle. Remove the drawer from the cabinet.
Locate the lock knockout plug on the file cabinet face. It is a scored oval typically positioned on the upper right corner of the file cabinet. Position the blade of a flat screwdriver in the center of the knockout, parallel to the widest section of the oval. Tap the end of the screwdriver with a hammer. Repeat until the plug pops out.
Insert the lock-cylinder into the hole to assess fit. If the hole is larger than the cylinder you will need to use the filler included with the kit. Remove the cylinder. Work from the inside of the cabinet and insert the filler into the knockout hole.
Insert the key into the lock-cylinder. Turn the key until the lock-bolt, located on the end of the cylinder, is in a vertical position. Insert the lock cylinder into the knockout, making sure the lock-bolt remains in a vertical position. Once the cylinder is in place, turn the key clockwise a quarter turn.
Secure the cylinder in place with your right hand on the outside of the cabinet. Hold the closed end of the retaining-clip in your left hand. Working from the left side of the cylinder, place the retaining-clip, with the prongs facing the cylinder, against the interior wall of the cabinet. Slide the retaining-clip over the cylinder. Check to be sure the prongs are lodged into the grooves located at the top and the bottom of the cylinder.
Hold the linkage-piece inside the cabinet with the pointed end aimed at the lock-bolt and the flat tab parallel with the top of the cabinet. Use a flashlight if needed. Locate the pre-drilled hole in the lock-bolt. Insert the point of the linkage-piece into the hole. Rotate the linkage-piece counterclockwise into a vertical position.
Insert the bottom square end of the linkage-piece into the lock-assembly located on the right side wall of the cabinet. Use a screwdriver to bend the end of the linkage-piece to secure it in place.
Check the installation by turning the key a few times. The lock assembly should rise to lock and lower to unlock. Replace the drawer.