TWO EMPLOYEE'S WERE IN THE PROCESS OF LOCATING BREAKS IN ROOF BY DRILLING 6' TEST HOLES. INJURED WAS DUCK WALKING THROUGH A WET AREA ALONG SIDE THE DRILL STATION OF BOLTER. AS CO-WORKER REPOSITIONED THE BOLTER FOR NEXT HOLE, INJURED TRIED TO POINT TO WHERE HE WANTED THE NEXT HOLE. HE LOST HIS BALANCE GRABBING THE ATRS CANOPY AT THE SAME TIME THE CANOPY CONTACTED THE ROOF.