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