received in a complimentary sized and configured recess 126 suitably formed in the rear surface 128 u2032 of the receiver frame 24 fig1 locking plate 102 further comprises a laterally extending integral tab 128 having an opening 130 for serving as an attachment point for a shoulder strap or sling as indicated by the dashed outline in fig1 the tab 128 and its defined opening 130 may optionally extend to the right or to the left depending upon the personal dictates of the user additionally as substantially depicted in fig1 and 14 locking plate 102 may be provided with a first female threaded recess 132 extending vertically through lower or bottom portion 116 in substantial alignment with tang 118 and intercepting curved supporting surface or seat 122 a first male threaded set screw 134 is threadedly engaged within first recess 132 and may be tightened against the castle nut 112 engaging supporting surface or seat 122 after the parts are assembled together by this action the locking plate 102 provides enhanced support for and secure locking engagement of the tightened down castle nut 112 locking plate 102 preferably includes a second female threaded recess 136 extending transversely through lower or bottom portion 116 for receiving a second male threaded set screw 138 second recess 136 aligns with a resilient detent 140 suitably seated in the frame 28 and which may be used conveniently for accessing the takedown pin when it is desired to pivot open the upper receiver from the lower receiver as is well.