Abstract: A mounting system for a sheet on a vehicle includes two elongate rub rails with undercut channels to receive the sheet and tensioning components. The upper rub rail is engaged with one of opposed edges of the sheet. An elongate engagement is engaged with the other opposed edge of the sheet and includes one frame rail and an engagement surface both facing the upper rub rail. An elongate retainer includes a bead engaged with the lower rub rail, another frame rail and parallel retainer surfaces, the second frame rail and the parallel retainer surfaces facing away from the upper rub rail. The engagement surface is movable laterally of the parallel retainer surfaces to be positioned in interlocking engagement with any one of the parallel retainer surfaces to tension the sheet.