the extension member is pivotably attached about the rotary shaft between {HEAD ~ the first position} and {TAIL ~ the second position}, 
the extension member is pivotably attached about the rotary shaft between { HEAD ~ the first position } and { TAIL ~ the second position } ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH