is positioned to align with the fastener boss 53 hole fig1 when the alignment dowels 55 57 extend through the panel 33 and the respective positioning holes 91 93 fig4 in the face of the female wing member 35 a rectangular receiving hole 95 at the far end of the body portion of the backer plate 39 receives the knuckle 61 projection to hold the cover 59 closed against the body the cover 39 is domed to permit a clearance for any fastener nut or head projecting from the back face of the backer plate body 87 fig6 shows the assembled hinge assembly 31 mounted on the panel 33 with the male wing member 37 rotated 180 degrees from the female wing member 35 the interlock hooks 75 77 can be seen engaging the far end 83 of the female wing member receiving barrel 49 a bolt 97 extends through the hole in the mounting boss 53 and is held fast with a nut 99 the backer plate 39 fig5 can take other shapes equally as well such as a rectangular box like structure 39 a fig7 this box like structure eliminates the need for a cover 59 fig5 but requires a fixed threaded stud 101 to be mounted to the face of this backer plate 39 a this box like backer plate 39 a includes a perimeter wall 103 of uniform height for rigidity a treaded receiving bore 104 is formed in the face of the backer plate 39 a fig7 for receiving and holding the stud 101 mounting brackets 105 107 hold the positioning pins dowels or tubes 55 57 respectively.