Abstract: A sign assembly for mounting on a motor vehicle includes a first and second panel mounted to left and right rear doors, respectively, of a cargo storage compartment in a motor vehicle. The panels have substantially parallel inner edges positioned adjacent when the left and right rear doors are closed, an interface of the inner edges substantially aligned with an interface of the rear doors when closed. A plurality of spacers are positioned between the panels and the rear doors, and the spacers are sized to position the panels substantially parallel with the rear doors and sufficiently spaced therefrom to provide clearance for a vertical locking bar assembly integral with at least one of the doors.