A mounting assembly for securing a bracket, to which a side skirt may be attached to a frame of a wheeled container chassis semi-trailer. The assembly includes a support and at least one resilient securement member. A proximal end of the support may be mounted in a substantially outwardly transverse horizontal orientation to one side of the semi-trailer; a distal end secures the bracket in a position to maintain the side skirt in a substantially vertical configuration between the frame and a ground surface on which the semi-trailer is situated and substantially in line with the wheels on the one side of the semi-trailer. The securement members mount the support to the frame. The support may move relative to the frame in response to an applied force and is biased to return and maintain the support in the substantially outwardly transverse horizontal orientation when the force is removed.