Abstract: A new and improved seam plate, for use in connection with securing roofing membranes to underlying roofing decking substructures, comprises a circular disk having a central aperture for receiving a screw fastener, a plurality of concentric ribs for providing reinforcing and bending or flexibility characteristics to the seam plate, and a plurality of circumferentially spaced, downwardly extending projections or eyehooks. Structure is provided upon the seam plate such that the downwardly extending projections or eyehooks, disposed upon, for example, a first one of a plurality of stacked or nested seam plates, are prevented from entering and becoming interlocked with openings or apertures defined within a second one of the plurality of stacked or nested seam plates.