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