Abstract: A foldable sign capable of being mounted on the roof of a vehicle. The foldable sign has a sign plate pivotally mounted upon a base which may be removably or fixedly secured to the roof of the vehicle. Interconnected between the sign plate and the base is a latching mechanism capable of securely locking the sign plate at two portions thereof in either an upright (unfolded) position or a horizontal (folded) position with respect to the base. The latching mechanism includes a movable rod which enables an individual with a single sliding movement of the rod to simultaneously disengage the latching mechanism from both portions of the sign plate. In so doing, it is possible to maintain a positive locking of the sign plate in either the upright or retracted positions while enabling a quick release of the locking action to be effected when desired.