Abstract: An assembly of metal panels for a building or the like, wherein adjacent panels have outwardly projecting side flanges interlocked to constitute a seamed rib, and including anchor clips mounted on supporting structure and held in the seamed rib between the interlocked flanges for securing the panels to the structure. The outer portions of the panel flanges are formed as longitudinal box channels all opening in the same lateral direction and dimensioned to interfit in nesting relation, while the clips similarly have portions formed as box channels that fit between the nested channels of the interlocked flanges. The channel-formed portion of each panel flange has an outer leg formed with a return curve; for ease of assembly, the return curve on the outermost flange of each seamed rib is initially partly open, and is deformed after assembly so as to conform closely to the return curve of the inner flange of the rib.