EE WAS WALKING AROUND 1B CONVEYOR HEADSECTON TO INSPECT RETURN IDLERS. HE NOTICED THAT SOMEONE HAD NOT REPLACED THE 24"" X 24"" GRATING TO THE ACCESS TO THE PLATFORM BELOW. INSTEAD OF REPLACING THE GRATING, HE WALKED ON A 9"" LEDGE BETWEEN THE HEADSCREEN AND THE FLOOR OPENING WHILE HE DID THIS HIS RIGHT FOOT SLIPPED, THEN HE HIT HIS LEFT SHIN ON GRATING, LACERATION REQUIRED 4 STITCHES