A pivotal shaft is inserted into shaft penetrating apertures formed in the hinge ledges so that {HEAD ~ the hair retainers} are pivoted about {TAIL ~ the pivotal shaft} 
are pivoted about
A pivotal shaft is inserted into shaft penetrating apertures formed in the hinge ledges so that { HEAD ~ the hair retainers } are pivoted about { TAIL ~ the pivotal shaft }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL