TWO WORKERS WERE ON THE ROOF OF SOME MATERIAL STORAGE BINS HELPING REMOVE SANDBLASTING POT. THE CRANE LIFTING THE POT WAS FULLY EXTENDED BUT ONE OF THE POT'S SUPPORT LEGS WAS CAUGHT BEHIND THE TOE PLATE ON THE EDGE OF THE BIN ROOF. ONE EMPLOYEE GRABBED THE LEG AND ATTEMPTED TO LIFT IT OVER THE TOE PLATE. AS HE DID SO THE POT SHIFTED & HIS FINGER WAS PINCHED BETWEEN LEG & TOE PLATE.