First of all, the pressing roller unit or {HEAD ~ a plurality} of such units is located at {TAIL ~ the appropriate location} or locations 
is located at
First of all , the pressing roller unit or { HEAD ~ a plurality } of such units is located at { TAIL ~ the appropriate location } or locations
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH