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 Joshua Jemison

Works particularly well when installing locks on both the bottom and top rails against a closed sliding window (or sliding door). I placed the bottom lock on the center rail for maximum effect on the door and window. I was able to install the insert and attach it to the rail at just over 0.2" thick, slightly more than the advertised 3/16". They didn't budge when I tried to force the panels open. When mounted 2 inches from a closed panel (to allow for a partially open window) I was able to get them to slip a little by repeatedly opening the window, but only a few millimeters or so at a time. An intruder would rather break the glass before you go to all that trouble.