TONNEAU COVER SYSTEM WITH INSERT FOR SUPPORTING CROSS-BOW MEMBERS

A frame rail assembly for supporting a tonneau cover comprising: opposing frame rails locatable on a cargo area of a vehicle, each of the opposing frame rails having one or more slots formed therein; and one or more inserts that fit within the one or more slots respectively; wherein the one or more inserts are shaped to fit substantially flush with a transverse cross-sectional profile of the opposing frame rails.