parts as a fastened fastener assembly 25 the male and female extrusions 30 and 31 are extruded in this case the fastener assembly 25 is secured with a mechanical u201c ball and socket u201d union a combination of a press fit and an interference fit as well as with a vacuum the female member 32 of female extrusion 30 accepts the male member 33 of male extrusion 31 to form a precision fit and a vacuum seal the corresponding features shaped into each mating part 32 and 33 actually force all of the air out of the cavity 35 of fastener assembly 25 and creates what is called the vacuum fit this special fit resists separation and bolsters the strength of the mechanical union between the two mating parts or extrusions 30 and 31 by mating surfaces 38 and 44 also because all of the air is removed from between the two parts female member 32 and male member 33 upon fastening any capillary action that would otherwise fill voids or the cavity 35 with water or other fluid is prevented another hermetic seal is produced between the two extrusions 30 and 31 fig3 b shows one of the female extrusions 30 by itself fig3 c shows one of the male extrusions 31 by itself fig4 shows a view from below an end cap 40 the end cap 40 is over molded onto the end of the zipper assembly 20 to form yet another hermetic seal in this view a cavity is visible where the assembly of two mating extrusions 30 and 31 fit together and are located upon molding the thickness of the flange on the end cap 40 is the same as the thickness of the flange.