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