a cam surface located on an exterior portion of {HEAD ~ the tieback member} in engagement with {TAIL ~ an inner side} of the locking member 
a cam surface located on an exterior portion of { HEAD ~ the tieback member } in engagement with { TAIL ~ an inner side } of the locking member
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH