INJURED EE & ANOTHER EE WERE REPLACING THE GUARD ON #19 CONVEYOR. INJURED EE WAS USING A CRESCENT WRENCH TO TIGHTEN THE NUT THAT HELD THE GUARD IN PLACE. THE WRENCH SLIPPED & STRUCK HIS HAND A GAINST THE EDGE OF THE GUARD RESULTING IN LACERATION TO TOP OF 2 FINGERS RIGHT HAND.