{HEAD ~ The one first side portion} may further comprise {TAIL ~ upper and lower first recessed sections} and the one second side portion may further comprise upper and lower second recessed sections 
comprise
{ HEAD ~ The one first side portion } may further comprise { TAIL ~ upper and lower first recessed sections } and the one second side portion may further comprise upper and lower second recessed sections
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH