Window screens let you welcome fresh air without inviting bugs or large amounts of dust and pollen into your home—but when one tears, it can't do its job. Check your windows to see if any need a quick fixing. If you find a spot in need of repair, all you need to do is stretch a length of screening over the metal frame and cut to size. Then insert a new spline into the frame using a rolling tool. Lastly, trim the excess material, and return the screen into the window frame.