EE WAS WORKING ON AN ELECTRICAL FAULT ON UNIT HU714/174. THERE WERE SOME ELECT. WIRES THAT NEEDED TO BE COVERED TO PROTECT THEM FROM RUBBING. HE WAS CUTTING ON A SHEET OF RUBBER TO WRAP AROUND THE WIRES USING A UTILITY KNIFE TO CUT WITH, THE KNIFE SLIPPED AND CUT HIS LEFT HAND BELOW HIS THUMB. STITCHES WERE REQUIRED.