The rail section has {HEAD ~ a profile} that provides {TAIL ~ one or more roller contact areas} extending a length of the rail section 
provides
The rail section has { HEAD ~ a profile } that provides { TAIL ~ one or more roller contact areas } extending a length of the rail section
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH