Review on Lion Locks Sliding Window and Door Locks (10 Pack), Adjustable Aluminum Security Screw Lock for 3/16-3/8” Track, Door Stopper Safety Lock, Easy Install, No-Drill Required, Requires 28-36mm Clearance for Screw Lock by Ulysses Fincher

This is fantastic! Installs two for each window. They are very simple, fast, effective and affordable! They fit snugly against the glass and the rubber grip provides a seal that ensures a secure fit without damaging or compromising the integrity of the case. fit exactly. They are small and do not fly out of the sash. They are designed with this in mind as they are INSIDE the wing. TIPS: 1. Use two locks - one on each side of the sash. Be sure to place them flush with the glass.2. Remove the rubber grommet to ease initial placement. Put the lock on the wing. Slide the rubber pad into position from the top.3. Hand-tighten the screws, and then tighten them with pliers. You'll be amazed at how many twists you can still do and how tight they become. When used with a latch you will get an impenetrable window when installed correctly. This means your window CANNOT open and offers optimal security. HIGHLY RECOMMENDED!