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