It consists of {TAIL ~ an array} of plates, serrated on an edge, and assembled in a block {HEAD ~ whose midline} is continuous with the entry to the fixed guide 
It consists of { TAIL ~ an array } of plates , serrated on an edge , and assembled in a block { HEAD ~ whose midline } is continuous with the entry to the fixed guide
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH 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 OTH