{TAIL ~ a third rail}, oriented perpendicular to {HEAD ~ said first and second rails}, and slidably mounted to said first and second rails 
{ TAIL ~ a third rail } , oriented perpendicular to { HEAD ~ said first and second rails } , and slidably mounted to said first and second rails
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH