Abstract: This invention relates to an improved sign which may be quickly and easily detachably secured to an automobile body by being inserted into the space between the trunk lid or front hood and the fenders of the automobile. The flat rigid sign is between 1/8 and 3/8 inches in thickness and may be formed of a corrugated cardboard panel sandwiched between two flat cardboard panels and covered by a smooth vinyl coating to be resilient to pressure from the side. It is attached to the automobile by being manually depressed into the vertical space until its lower edge abuts on a horizontal portion of one of the members forming the space, in which position it is retained substantially vertically by being resiliently engaged between the sides of the space. In a preferred embodiment, the sign has a flexible lower edge portion provided by the vinyl covering extending downward beneath the cardboard panels, which is bent sideways to engage one of the members defining the space.