EE WAS HELPING ANOTHER EE UNLOAD A SHEET OF FLOOR GRADING (36"" WIDE X 20' LONG) OFF THE BED OF A PALLET TRUCK. EE LOST CONTROL OF THE GRADING WITH HIS LEFT ARM AND THE FULL WEIGHT OF THE GRADI NG CAME OFF THE TRUCK AND, ACCORDING TO EE, HIS RIGHT ARM ABSORBED THE FULL WEIGHT OF THE GRADING. THE OTHER EE STILL HAD HIS END OF THE GRADING SUPPORTED. EE DID NOT REPORT THE INCIDENT UNTI