We have an older home, with some of the screens that needed to be secured. Normal fasteners attach between the rubber that secures the screening material and the screen frame itself. They are very difficult to put in, and easy for our son to remove. We used a medium sized office binder clip to secure the screen to the window sill.
We tried this after ordering a similar product that wasn't the right size. We needed something a little larger. This is much more economical, and easy to do - hope this helps someone :)