Abstract: A device provided with its own power supply to be hooked up to the lighting system on a vehicle trailer, such as semi-trailers, campers, mobile homes, and the like, for the purpose of flashing all or some trailer lights on and off while the trailer might be left unattended at the side of a road so as to warn passing motorists of its presence. The unit consists of a dry cell battery, a conventional flasher mechanism, an on-off switch, a mounting plate provided integrally with a handle therewith, and a plug adapted to fit a vehicle trailer lighting system. The device is portable and can be easily connected or disconnected to a vehicle trailer so that it can readily be stored in the towing vehicle when not in use or it can be readily relocated from one trailer to another.