Review on Enhanced Vinyl Sliding Window Locks by Defender Security - Effortless Installation for Securing Windows - Durable White Diecast Construction (Pack of 2) by Cesar Danger

I have fitted these to the bedroom windows in the children's rooms. I put 2 on each window (1 on each side). I let about 3 inches of air through but no one can get in. This is better than bars on the windows as the bars cannot be removed in the event of an emergency/fire. I feel much calmer when I go to bed knowing that my children will be there in the morning and no one can enter. I've bought a few more so far. Here is some useful information: I myself use it on double windows. So if you look at the picture of a small lock, you will see a square at the top, a turning handle at the front, and a hidden piece at the back that moves back and forth. You take the lock and open this sliding part by turning the handle. You open it wide enough for the lock's "teeth" to fit into the window frame. (See photo) It can be attached to any frame as long as the frame is thin enough to fit in your teeth. The teeth open about 1/2 inch, so if the frame you want to attach to is 1/2 inch thick or thinner/less then you're good to go. Put it on the frame (see picture) and turn the knob to tighten it. Once you've secured it nice and tight, push the handle down and that will secure it even more. Note: Be sure to use BOTH locks on the same window. In testing, I placed a lock so the window opened 3 to 5 inches. Then I "pretended" to get in, grabbed the window from underneath and pushed it up pretty hard. I've done this a few times, and by rocking the window up and down, I'm able to slowly but noisily raise the lock an inch until there's enough room to climb in the window. However, this is very difficult when using BOTH locks on both sides of the window. Having two in place is a pretty safe situation. I also like that I don't have to screw them in anywhere, which not only damages the window frame but only allows for one position. So you can always move them up and down or just delete them. This means you can place them with the window opening 3 or 4 inches or almost fully open or almost fully closed wherever you like and you can change it from day to day if you like. . Nothing permanent. I like it! Sorry for some photos. Revane wouldn't let me flip a few of them. Hope this still helps.