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