If you have windows that can open and close, odds are there is some sort of locking mechanism that prevents unwanted entry. Just like anything with moving parts, a window lock can become damaged over time. When this occurs, you will need to replace it as soon as possible. Replacing locks is one of the fastest window repairs you'll ever do.
Unscrew the broken lock from the window frame and the sliding portion. Remove the screws and lock pieces from their positions.
Place the lock strike plate on the window frame cross bar in the same location as the old strike plate. Mark the location of the screw holes with a pencil. If the screw holes for the new strike plate do not match up, you will have to drill new holes for the strike plate with the 3/16-inch bit.
Drill holes in the window frame if necessary for the strike plate. Place the strike plate back on the window cross beam and screw it into place using the Phillips head screwdriver and the screws that came with the lock kit.
Place the locking mechanism on the window in the same location as the locking mechanism that was broken. Mark the screw holes with the pencil to determine if they line up. Drill holes at your marks if you need new holes.
Place the locking mechanism over the window screw holes and screw it to the window with the screws that came with the locking kit.