{HEAD ~ The front cover} is movably mounted on {TAIL ~ the base} and has a rear surface and a transverse slot formed on the rear surface 
is movably mounted on
{ HEAD ~ The front cover } is movably mounted on { TAIL ~ the base } and has a rear surface and a transverse slot formed on the rear surface
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH