How to secure an open window?

I’d like to be able to leave my garden level windows open a few inches for air while I’m out of the house (or at night) and not worry about them being opened further from the outside. I’ve been wondering if there’s a product or some way to secure them on the inside so they’re several inches open. The windows are old and don’t have that newer security feature that pops out to prevent the window from being opened all the way. New windows aren’t an option at this point unfortunately. If anyone has any ideas or tricks please let me know.

By herkimermaid |