I am looking to buy locks or clasps that can be screwed attached or bolted to windows and sliding doors to prevent kids from opening the windows. I have found one of these on a window at home. It’s a block of plastic with a chamfer that mates with the groove on the slide rail on the window frame. The block of plastic has a hole in it and is screwed down onto the window rail. Pretty simple but clever
The window can be opened slightly allowing fresh air in, but not so much that something could get or fall out. You can adjust the location of the block.
These are cheap and crude but effective, but neither I nor my wife can find out where these were bought. I was thinking you can probably buy such things in IKEA and B&Q
I got mine at those stores that sell Japanese-style trinkets and such, usually really cheap. No screwing necessary, just pressure and a stick on. Of course, mine are cruitters of the furry kind.
Got some others from Mitsukoshi, at the children’s clothes department, but they were not really such good quality, believe it or not the cheaper ones lasted more and were stronger. However, they still play the part.
We have metal ones that clamp onto the aluminium window frame. Simple but effective. Easily removable by an adult but not by a little kid I think. I’ll ask the wife where they came from.