Ron Hazelton describes how to replace a screen in a door or window. The screen is held in the frame by a vinyl cord that can be removed with a knife. Lift the old screen out of the frame. With the new screen on a flat surface, using the frame as a template, cut the new screen a half-inch larger than the frame all around. Cut 45-degree notches in the screen at each corner. Place the screen evenly on the frame. Press the cord back into the groove on the sides first, then the top and bottom. Finally, trim off the excess cord and screen.