Abstract: A cover or envelope having one open end fits over a traffic sign to cover the sign and its message; new information is presented to motorists by appropriate indicia on a front outer surface of the envelope. A rear side of the envelope includes a slit in its center; the slit extends most of the length of the back side and opens to accommodate the bulk of a post or standard on which the sign is mounted. At the bottom, open edge of the cover, metal rods are incorporated into hems on the cover's edge and have protruding loops or tabs thereon; the loops receive a padlock or other means by which the cover is secured in place over the signboard to prevent the cover's unauthorized removal. For a diamond-shaped signboard, two perpendicular slits divide the rear of the cover into triangular panels.