Plastic fastener

Claim 1

A RESILIENT ONE PIECE PLASTIC FASTENER IN COMBINATION WITH A WORKPIECE HAVING AN APERTURE OF PREDETERMINED CONFIGURATION AND TRANSVERSE DIMENSION, SAID FASTENER INCLUDING A SHANK AND A LATERALLY EXTENDING HEAD AT ONE END OF SAID SHANK, SAID HEAD PROVIDED WITH AN AXIALLY EXTENDING COUNTERBORE THROUGH SAID HEAD AND FOR A PREDETERMINED DISTANCE INTO SAID SHANK AND DEFINING IN TRANSVERSE SECTION AN OVAL WITH MAJOR AND MINOR AXES, A SECOND BORE PROVIDED IN SAID SHANK OF SMALLER TRANSVERSE DIMENSION THAN SAID COUNTERBORE AND HAVING ITS LONGITUDINAL AXIS WHICH IS COINCIDENT WITH THE LONGITUDINAL AXIS OF THE COUNTERBORE IN SAID HEAD, SAID SECOND BORE COMMUNICATING WITH SAID COUNTERBORE AND DEFINING IN TRANSVERSE SECTION AN OVAL WITH MAJOR AND MINOR AXES ROTATED 90* RELATIVE TO THE MAJOR AND MINOR AXES OF SAID COUNTERBORE, SAID SHANK IN TRANSVERSE SECTIONS SPACED ALONG ITS AXIS PRESENTING A FIRST PORTION HAVING A CONTINUOUS THIN WALL SECTION IN THE VICINITY OF SAID HEAD AND A SECOND PORTION HAVING A THICKER WALL SECTION OF SUBSTANTIAL AXIAL EXTENT AND EXTENDING FROM SAID FIRST PORTION TO THE VICINITY OF THE TERMINAL END PORTION OF SAID SHANK, THE OUTER SURFACE OF SAID SHANK IN THE VICINITY OF SAID LATERALLY EXTENDING HEAD HAVING A COMPLEMENTARY CONFIGURATION TO THE COUNTERBORE PROVIDED IN THE SHANK SECTION ADJACENT SAID HEAD WITH ITS MAJOR AND MINOR AXES IN A SUBSTANTIAL REGISTRY WITH THE MAJOR AND MINOR AXES OF SAID COUNTERBORE, THE WALLS OF SAID WORKPIECE APERTURE FORMING A SUBSTANTIALLY CIRCULAR SURFACE ADAPTED TO CONTACT A PORTION OF SAID OUTER SHANK SURFACE IN THE VICINITY OF SAID LATERALLY EXTENDING HEAD WHEN THE FASTENER IS FINALLY POSITIONED IN THE WORKPIECE APERTURE, THE OUTER SURFACE OF SAID SHANK AROUND SAID SECOND BORE GENERALLY DEFINING AN OVAL IN TRANSVERSE SECTION GENERALLY COMPLEMENTARY TO SAID SECOND BORE, SAID WORKPIECE APERTURE BEING SO DIMENSIONED AS TO DEFORM THE WALL SECTION OF THE ENTERING END OF THE FASTENER AS IT PASSES THROUGH THE WORKPIECE APERTURE AND TO DEFORM THE THINNER WALL SECTION OF SAID SHANK IN THE VICINITY OF SAID HEAD TO FORM RETAINING SHOULDER MEANS WHEN THE FASTENER IS IN FINALLY MOUNTED POSITION RELATIVE TO THE APERTURED WORKPIECE AND THE WALL SECTION OF THE ENTERING END OF SAID SHANK PORTION HAS RETURNED TO ITS NORMAL DIMENSION AFTER THE TEMPORARY DEFORMATION OF IT BY SAID WORKPIECE APERTURE.