INJURED & 2 CO-WORKERS WERE PUTTING PIECES OF TIN ON THE ROOF OF THE BUILDING. ONE WAS HANDING THE TIN TO OTHER WHO WAS IN THE BED OF THE TRUCK & HE WAS HANDING THEM TO INJURED (WHO WAS ON TOP OF THE CAB OF THE TEREX TRUCK). MOST OF THE PIECES WERE 8' IN LENGTH. INJURED HAD TURNED TO PUT ONE PIECE OF THE ROOF. HE TURNED TO GRAB THE NEXT PIECE THAT WAS 12'LONG & RAN INTO IT CUT NOSE