{HEAD ~ A pair} of parallelly disposed vertical trollies are attached to the side of the building on {TAIL ~ opposite sides} of a plurality of emergency exits 
are attached on
{ HEAD ~ A pair } of parallelly disposed vertical trollies are attached to the side of the building on { TAIL ~ opposite sides } of a plurality of emergency exits
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH