DIESEL MECHANIC WAS REQUESTED TO CHECK THE OPERATION OF THE GEAR SHIFTER ON THE NO.9902 DART HAULAGE TRUCK. AFTER MAKING HIS CHECK HE EXITED THE TRUCK OPERATOR CAB AND WAS PREPARING TO DESCEND DOWN THE TRUCKS LADDER. AT THAT TIME THE TRUCKS OPERATOR CLOSED THE DOOR, NOT KNOWING HIS RIGHT HAND WAS ON THE DOOR POST, THIS PINCHED RIGHT MIDDLE FINGER, PARTIALLY REMOVING FINGER NAIL.