{HEAD ~ Each sidewall} has {TAIL ~ upper and lower portions} horizontally offset from one another with a connecting bridging member forming an arm rest 
has
{ HEAD ~ Each sidewall } has { TAIL ~ upper and lower portions } horizontally offset from one another with a connecting bridging member forming an arm rest
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH