a sensor mechanism for scanning the ends to determine whether {HEAD ~ each end} extends parallel to {TAIL ~ the path} without regard to the length of the piece being scanned; and 
extends parallel to
a sensor mechanism for scanning the ends to determine whether { HEAD ~ each end } extends parallel to { TAIL ~ the path } without regard to the length of the piece being scanned ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH