providing a structure including framing members and {HEAD ~ a sheath} forming {TAIL ~ at least one cavity} having a known depth 
providing a structure including framing members and { HEAD ~ a sheath } forming { TAIL ~ at least one cavity } having a known depth
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH