Each hair retainer has {HEAD ~ a pair} of opposing hinge ledges at {TAIL ~ one end portion} thereof 
at
Each hair retainer has { HEAD ~ a pair } of opposing hinge ledges at { TAIL ~ one end portion } thereof
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH