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