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