Things You'll Need
Drill with bits
One way to keep your home secure is to ensure that your window locks operate correctly. Fix or replace window locks that have damage or are loose. Fixing window locks often comes down to simply replacing the window lock. Window locks are available at home improvement centers with all the necessary hardware to install the lock. If purchasing replacements to fix the window locks, choose locks that have keys. These cannot be opened by an intruder simply breaking your window glass.
Tighten loose screws with a Phillips-head screwdriver. Correct any bends on either piece of the lock with a pair of needle-nose pliers. If the mounting area has damage but the lock is in good condition, relocate the lock position.
Remove the screws securing both pieces of the lock to the window with a Phillips-head screwdriver. Fill the mounting holes with wood putty, if you have a wooden window frame. Allow the putty to dry and sand the area with a fine-grit sandpaper until the putty is flush with the frame. If you have vinyl or metal windows, use wider window locks to cover the existing mounting holes.
Place the keeper portion of the lock on the top of the lower rail of the upper window sash. On casement windows, place the keeper on the top of the bottom rail of the window. The keeper is the narrower portion of the lock that the thumb lock portion hooks under. If possible, place the lock where the original lock was located. If necessary, move the lock left or right to avoid the previous mounting holes.
Mark the mounting hole locations with a pencil. Drill pilot holes for the mounting screws, using a bit slightly smaller in diameter than the screws. Place the keeper into position and secure with the mounting screws.
Place the thumb lock on top of the top rail on the lower sash, or top of the window sill for a casement window. Position the lock under the keeper. Mark the mounting holes with a pencil. Drill pilot holes for the mounting screws and secure the thumb lock with the mounting screws.
Although the window thumb lock is the popular choice for a window lock, many other styles are available. Refer to the manufacturer's instructions when installing specialty window locks.