One side or {HEAD ~ both sides} of {TAIL ~ the panel} 20′″ may be covered with a layer, such as an outer covering layer 
of
One side or { HEAD ~ both sides } of { TAIL ~ the panel } 20′″ may be covered with a layer , such as an outer covering layer
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH