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