{TAIL ~ A plurality} of {HEAD ~ rollers} are fixably and independently mounted in each of said channel members 
{ TAIL ~ A plurality } of { HEAD ~ rollers } are fixably and independently mounted in each of said channel members
TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH