Prime-Line U 9927 Keyed Sash Lock, Child-Proof Security Lock Only Unlocks w/ Key, For Aluminum, Vinyl or Wood Double-Hung Windows, 2” Hole Centers, Heavy-Duty Zinc, Brass Plated (Single Pack)

The product is well built, but the ease of closing it depends on installation. The two sides need to align perfectly. This is more tricky than it seems because the sliding window might not be flushed with the frame bar. In such case, add a shim to make it flush. Alignment issue is the reason why phillips screws are included in addition to the one-way tamper resistant screws. It might seem unnecessary to use the phillips screw first only to be removed and replaced with the one-way screws. But don't skip this important step because once the one-way screws go in, you can't remove them to adjust the alignment.If you made mistake in drilling, or if you're replacing an existing lock and the old screw holes are not at the exact same location, you can easily cover up the old holes with Bamboo Skewer and wood glue. Then a new hole near can be drilled right next the old one without breaking up the wood. Drilling pilot holes is strongly recommended because it's so easy to crack near the edge.The way the key works is slightly strange. There's no need to turn the key. Instead, just insert the key straight in, and then flip the latch open.There's another Prime-Line U 9933 that has a thinner left side. Check out how much room you have on the window before buying.

Really simple solution to adding some security for my windows. Works best when the 2 mounting surfaces are the same height and align. There is only a single position for lock and unlock. When your surfaces match it is very smooth and easy to lock and unlock.

Could be super dangerous. The lock only functions with the key in itMy intention was to purchase them and leave them unlocked and then lock them for safety if I went away for vacation or somethingHowever you cannot even unlock the window or lock it uness the key is in placeIf you lose the key and there's a fire you're locked in your bedroom or if your child breaks the key off in the lock and there's a fire they're locked in their bedroomAmazon Stood buy this product and their customer service was wonderful but I wanted to review this so potential buyers would think about this before they put them on their windows

This worked for what I needed but it was a little to big I can't use it as your supposed to the window ain't coming open anymore tho so that's all I needed I have a 2 4 and 6 year old that kept taking the entire window out up stairs and throwing things out I'm just thankful they didn't throw each other out but this has solved the problem

Makes sure you measure when you want to use these before you buy these. I’m sure all the macho handiman and internet Trolls will bash me with “Duh” and “no kidding sweet cheeks”Because of my son’s elopement issues I had to install these on his windows. I don’t mean he keeps trying to elope with some woman. I mean my son is Autistic and tried to climb out his bedroom window one night. Every special needs parents nightmare.I installed these and the back part is like a millimeter to wide and it covers the 2 frames so now even when I unlock it I can’t open the window.I can’t return the ones I have. I have to find something with a slightly narrower back side to fit my son’s windows.I’m not a particulary handy person so trying to screw these in was a pain for me. Maybe it won’t be if someone is more handy.

These keep the window closed. So I can't complain about that, but they were very difficult to install. They are about 1/4 inch shorter than my windows original locks but 1/2 inch wider. The key can't be removed unless the lock is fully in the locked or unlocked position, so I had to drill the screw in while the key was in the lock making the process require 3 hands, and more than a basic knowledge of drills. The other downside at least for me is, all the locks and keys look identical, but they aren't. I bought 4 locks and each one has a different key. This is mildly confusing, although I can see why they would be unique. Now that they are installed I have no complaints. My kids can't unlock the windows upstairs, so my windows stay shut, and the kids stay off the roof.

I ordered these to keep my five-year-old from crawling out the windows. They were easy to install my only issue is keeping up with all the keys and determining which one goes to which lock.

…. But don’t buy this for security. I got 10. And all of them had lose key cylinders, I had to tighten them with a wrench before installing. Since then, they’ve all loosened just from opening and closing. So I have to unscrew them and retighten, maybe use thread lock. Also, the mounting screws are short and kinda cheap, so don’t expect them to hold up to a dude with a crowbar.. no way, not gonna happen.