Abstract: A signal device for use on rural mailboxes comprises a substantially flat base and a lower flap. The flat base has a roof extending outwardly from the upper front surface and a protrusion, both of which aid in preventing the lower flap from freezing to the flat base under adverse weather conditions. The device is operational by gravity and is automatic. An adhesive is provided on the back surface of the flat base for ready installation of the device to existing mailboxes.