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