Bridges or webs are typically provided at {HEAD ~ different elevations} to define {TAIL ~ the cavities}, which may be cored 
to define
Bridges or webs are typically provided at { HEAD ~ different elevations } to define { TAIL ~ the cavities } , which may be cored
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH