{HEAD ~ Each} of the guide rails comprises {TAIL ~ an end} proximate to the aerosol valve and an end distal from the aerosol valve 
comprises
{ HEAD ~ Each } of the guide rails comprises { TAIL ~ an end } proximate to the aerosol valve and an end distal from the aerosol valve
HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH