{HEAD ~ The primary purpose} of the guide rails is to maintain {TAIL ~ the envelope} in a vertical position after the envelope has impinged against probe 21 and until proper disposition of the envelope is accomplished 
is to maintain
{ HEAD ~ The primary purpose } of the guide rails is to maintain { TAIL ~ the envelope } in a vertical position after the envelope has impinged against probe 21 and until proper disposition of the envelope is accomplished
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH