{HEAD ~ The swinging end} slides on {TAIL ~ a surface} of the interlocking member as the swinging of the interlocking member 
slides on
{ HEAD ~ The swinging end } slides on { TAIL ~ a surface } of the interlocking member as the swinging of the interlocking member
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH