At a third position in which {HEAD ~ the stem} is further pulled by one step from {TAIL ~ the second position}, it may also be turned, by an appropriate angle, in both directions 
At a third position in which { HEAD ~ the stem } is further pulled by one step from { TAIL ~ the second position } , it may also be turned , by an appropriate angle , in both directions
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH REL OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH