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