A three-piece locking fastener, comprising: an intermediate component having a one piece body with an exterior surface and an enlarged polygonal shaped head, a first hollowed interior extending between opposite ends, said intermediate component including a plurality of interior threads arrayed in a first direction and extending from a first of said opposite ends, a recess defined within said enlarged polygonal shaped head and extending inwardly from the other of said opposite ends and terminating in an undercut ledge, a polygonal inner perimeter configured in said recess and communicating said first hollowed interior with said undercut ledge; a first fastener having a further one piece body with a first enlarged head and a first stem with a second hollowed interior, a first exterior thread pattern configured on said first stem extending in the first direction for rotationally inter-engaging with said interior threads of said intermediate component when installed through said first selected one of said opposite ends, said second hollowed interior of said first fastener exhibiting a further plurality of interior threads extending in a second direction that is opposite to the first direction; and a second fastener having a second enlarged head and a second stem, upon which is configured a second exterior thread pattern extending in the second direction and, upon being installed through said enlarged polygonal shaped head and within the other selected one of said opposite ends of said intermediate component, said polygonal inner perimeter communicating said second stem within said intermediate component and in engagement with said hollow threaded interior of said previously installed first fastener, with said second enlarged head being received within said recess and against said undercut ledge, said second fastener rotationally inter-engaging said interior threads of said first fastener in the second direction, with loosening of either of said first and second fasteners (14, 16) being prevented. an intermediate component having a one piece body with an exterior surface and an enlarged polygonal shaped head, a first hollowed interior extending between opposite ends, said intermediate component including a plurality of interior threads arrayed in a first direction and extending from a first of said opposite ends, a recess defined within said enlarged polygonal shaped head and extending inwardly from the other of said opposite ends and terminating in an undercut ledge, a polygonal inner perimeter configured in said recess and communicating said first hollowed interior with said undercut ledge; a first fastener having a further one piece body with a first enlarged head and a first stem with a second hollowed interior, a first exterior thread pattern configured on said first stem extending in the first direction for rotationally inter-engaging with said interior threads of said intermediate component when installed through said first selected one of said opposite ends, said second hollowed interior of said first fastener exhibiting a further plurality of interior threads extending in a second direction that is opposite to the first direction; and a second fastener having a second enlarged head and a second stem, upon which is configured a second exterior thread pattern extending in the second direction and, upon being installed through said enlarged polygonal shaped head and within the other selected one of said opposite ends of said intermediate component, said polygonal inner perimeter communicating said second stem within said intermediate component and in engagement with said hollow threaded interior of said previously installed first fastener, with said second enlarged head being received within said recess and against said undercut ledge, said second fastener rotationally inter-engaging said interior threads of said first fastener in the second direction, with loosening of either of said first and second fasteners (14, 16) being prevented.