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