Large and small cannisters are provided at {HEAD ~ the respective ends} of {TAIL ~ a pivotable frame} 
of
Large and small cannisters are provided at { HEAD ~ the respective ends } of { TAIL ~ a pivotable frame }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL