Screw with cavity head

Claim 1

IN COMBINATION, A SHEETED MATERIAL HAVING TOP AND BOTTOM SURFACES AND A HOLE THERETHROUGH, A STUD INCLUDING A HEAD AND A SHANK, SAID SHANK EXTENDING THROUGH SAID HOLE, SAID SHANK HAVING A THREADED PORTION SPACED FROM SAID HEAD, SAID SHANK HAVING FIRST AND SECOND UNDERCUT ANNULAR RECESSES BETWEEN SAID THREADED PORTION AND SAID HEAD, SAID FIRST RECESS BEING CLOSER TO SAID THREADS THAN SAID SECOND RECESS, SAID HEAD BEING DRIVEN INTO SAID SHEET FLUSH WITH THE TOP SURFACE THEREOF, A PORTION OF THE MATERIAL OF SAID SHEET ENCOMPASSING SAID STUD BEING DISPLACED AND FORCED BY SAID HEAD TO FLOW DOWNWARDLY AND RADIALLY INWARDLY TOWARD SAID RECESSES, THE VOLUME OF SAID FIRST RECESS BEING LARGER THAN THE VOLUME OF SAID SECOND RECESS, AND AN ANNULAR BEAD ENCOMPASSING AND EXTENDING INTO A PORTION OF SAID FIRST RECESS AND FORMED BY SAID FLOWING MATERIAL, SAID BEAD DEPENDING FROM THE BOTTOM SURFACE OF SAID SHEET METAL BODY, AND SAID BEAD FILLING AT LEAST A PORTION OF THE FIRST RECESS.