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