Anyone know how to get the pop out windows to stay open?

I know it kills me, I have looked and looked at them, and for the life of me I can't figure out how to tighten them up! The Indiana heat is getting to me...and I'm sure the air would circulate a lot better if those windows would stay open. I flattened the clip in the middle out a little bit, and it helped, but it still doesn't feel like it "clicks" into place.