{HEAD ~ A protective wall} extends from the base and is spaced from {TAIL ~ the first sidewall} 
is spaced from
{ HEAD ~ A protective wall } extends from the base and is spaced from { TAIL ~ the first sidewall }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL