INJURED WAS OPERATING ROOF BOLTING MACHINE ALONGWITH ANOTHER EMPLOYEE. UPON ENTERING THE AREA, THEY FOUND THE RIBS TO BE IN GOOD CONDITION. AFTER INSTALLING 3 ROWS OF BOLTS, THEY ADVANCED TO INSTALL THE FOURTH. INJURED HAD POSITIONED THE MACHINE & DRILLED THE BOLT HOLE WHEN A SECTION OF ROCK & COAL FELL FROM THE RIB PINNING HIS LEGAGAINST THE MACHINE AND FRACTURING HIS ANKLE.