EMPLOYEE WAS WORKING WITH CREW BUILDING CRIBS. THEY WERE RELAYING CRIBS FROM ONE POINT TO ANOTHER. IN DOING SO INJURED WAS PLACING A CRIBON BOTTOM AND WAS STRUCK BY A 2ND CRIB BEING PASSED BY ANOTHER WORKER; NO MINING EQUIPMENT WAS INVOLVED OR SAFETY RULES BROKEN; NO PROTEC- TIVE DEVICES COULD HAVE AVOIDED ACCIDENT, BUT WORKERS COULD HAVE PAYED CLOSER ATTENTION TO