Opaque window shades of semirigid material, developed for blackout, have an outward surface of black, while a cheerful ivory finish faces the interior. By a corrugating process the shade is given a one-way rigidity that permits rolling and unrolling and keeps the edges snug against the window frame to prevent light leaks. In its simplest form the shade may be fastened to the window frame by means of adhesive tape. A more convenient installation may be made by fastening one end fo the top of the window by means of slats, and rolling the shade upward from the bottom where it is fastened to another slat. When not in use the shade remains tied at the top with a cord.