EMPLOYEE WAS USING A KNIFE TO REMOVE A PLASTIC WINDOW COVERING TO ALLOW MORE VENTILATION TO PASS THROUGH THE WORK AREA. WHILE CUTTING THE PLASTIC AT THE TOP OF THE WINDOW AND PULLING THE KNIFE BLADE TOWARD HIM, THE KNIFE BLADE PASSED OVER THE TOP OF HIS THUMB ON HIS LEFT HAND RESULTING IN A LACERATION APPROX 1 INCH IN LENGTH. WAS WEARING COTTON GLOVES.