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