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