retained on the tailgate 12 in any suitable conventional way preferably by frictional engagement of the arms 14 16 with the tailgate 12 across the entire width thereof and may be made of any suitable material such as a molded high impact plastic it has been found desirable to extend the inner arm 16 substantially to the truck bed as shown in dashed lines in fig1 the additional height provided when the tailgate approximates the thickness of a truck bed liner and reduces the risk of interference with the unloading of cargo this extension also provides the opportunity to insert a conventional fastener such as a self tapping metal screw through the extension into the tailgate as a safety measure the deflector extends rearwardly from the tailgate 12 to form a spoiler for the air exiting the truck bed and then downwardly to form an elongated cavity or slot between the arms 18 and 14 that extends across the width of the tailgate 14 a shaft 20 is journaled for rotation about the longitudinal axis thereof within the slot and is provided with suitable conventional means at one or both ends thereof for rotationally biasing the shaft a suitable flexible material 22 such a sheet of high tensil strength plastic desirably reinforced with glass or metal fibers or a tightly woven fabric is fixedly attached to the shaft 20 and wound thereon by the rotational bias applied to the shaft the free end of the material 20 may be provided with an enlarged stop to limit the rotation of the shaft and provide ready finger access to the material 22 so that it may be withdrawn from the slot against the.