A metal cover, whose shape may trace {HEAD ~ the shape} of {TAIL ~ the rib}, may be interposed between the rib and the groove 
of
A metal cover , whose shape may trace { HEAD ~ the shape } of { TAIL ~ the rib } , may be interposed between the rib and the groove
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH