{HEAD ~ Each side rail portion} includes a horizontal wall between the inner wall and {TAIL ~ the mid wall} 
{ HEAD ~ Each side rail portion } includes a horizontal wall between the inner wall and { TAIL ~ the mid wall }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL