Each roller assembly 43 comprises {TAIL ~ an upper roller} 45 and a lower roller 46, with a power source 44 for rotating {HEAD ~ the upper rollers} 45 
Each roller assembly 43 comprises { TAIL ~ an upper roller } 45 and a lower roller 46 , with a power source 44 for rotating { HEAD ~ the upper rollers } 45
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH