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