A clamp assembly for mounting a tonneau cover on a motor vehicle having a cargo area defined by first and second side walls, an end wall and a tailgate, the side walls having an inner panel and an outer panel includes a fastener, a first coupler plate and a bracket. The first coupler plate has a first end and a second end. The first coupler plate is articulable from an operable position to a disengaged position. The bracket has a generally horizontal rail and a vertical rail. The bracket is adapted for contacting the outer panel of the first side wall and further has a seat pivotally retaining the first end of the first coupler plate. The second end of the first coupler plate is adapted for engaging the inner panel of the first side wall defining a first restraining area between the horizontal rail and the second end of the first coupler plate. A second restraining area between the vertical rail and the second end of the first coupler plate is also defined. The fastener detachably interconnects the first coupler plate and the bracket when the first coupler plate is in the operable position.