An aerodynamic reducer for a trailer comprising one or more sheet members which are secured to the lower ends of at least some of the cross-members positioned beneath the floor of the trailer. The step structure comprises two non-rectangular surfaces, such as the trapezoid or triangular surfaces, and a rectangular surface. A pair of side supports may be joined to the base member on opposite sides of the bed. Also disclosed herein is a method for removing foreign material from an upwardly oriented surface of a body-in-white that comprises using bringing the apparatus defined herein in proximate contact with at least one surface of a body-in-white as it progresses down a vehicle assembly line.