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