Our window sashes slide horizontally--90 degrees from the traditional windows shown in the illustration. But I can make them work for our house, especially windows on the west side where the pollen blows in. I first bought screens of this design a couple of decades ago from another catalog, just to keep the summer rain out and still have moving air. As I have become more allergic to dust mites and pollen over the years, the screens and the replacement filters have become more important to our warm weather house maintenance. I briefly considered the Pollentec option, when one exterior screen needed total replacement after a bad storm. But with these screens, I can take care of 7 windows instead of 2, for less cost.