The anchor is an elongate cylindrical shell with a central passage to receive {HEAD ~ the bolt}, thereby forming {TAIL ~ an anchor bolt unit} 
forming
The anchor is an elongate cylindrical shell with a central passage to receive { HEAD ~ the bolt } , thereby forming { TAIL ~ an anchor bolt unit }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL