The invention provides a system for installing a load on a metal panel roof, the system comprising a rail and closure structure adapted to be supported by ribs defined by the roof panels, and a load adapted to be supported on the rail and closure structure. In some embodiments, standing seams on ribs, and side rails on the rail and closure structure, extend parallel to each other, and optionally parallel to opposing sides of a hole in the roof. In some embodiments, substantially all of a downwardly-directed force of the load passes downwardly through the rail and closure structure to the ribs, and from the ribs to underlying structural members of the building.