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