1. A METHOD OF MAKING A PRE-ASSEMBLED FASTENER UNIT COMPRISING PROVIDING A NUT MEMBER HAVING A CLAMPING FACE AND AN ANNULAR SKIRT PROJECTING FROM SAID CLAMPING FACE AND HAVING A SUBSTANTIALLY CYLINDRICAL OUTER SURFACE AND AN OUTWARDLY FLARING INNER SURFACE, PROVIDING A PIECE OF SHEET MATERIAL STOCK OF PREDETERMINED THICKNESS FOR A WASHER AND SUPPORTING SAID PIECE OF SHEET MATERIAL STOCK ALONG AND ANNULAR AREA THEREOF AND LEAVING A PORTION OF THE SHEET MATERIAL STOCK WITHIN SAID AREA UNSUPPORTED, THEN DRAWING AND FORMING SAID PORTION OF THE SHEET MATERIAL STOCK AND THEREBY PROVIDING A CENTRAL CUP-SHAPED SECTION SURROUNDED BY AN ANNULAR SECTION SUBSTANTIALLY INCLINED AWAY FROM THE REMAINDER OF THE SHEET MATERIAL STOCK, THEN SUPPORTING SAID ANNULAR SECTION AND PUNCHING SAID CUP-SHAPED SECTION FROM SAID STOCK MATERIAL AND THEREBY PROVIDING AN APERTURE HAVING A SUBSTANTIALLY CYLIN-