second mounting means disposed on said trap for alternately mounting {HEAD ~ said trap} on {TAIL ~ a horizontal wall} of said furnace 
on
second mounting means disposed on said trap for alternately mounting { HEAD ~ said trap } on { TAIL ~ a horizontal wall } of said furnace
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH