WHILE DRILLING A BOLT HOLE, 9 1/2"" THICK PIECE OF DRAW ROCK SLATE BROKE LOOSE FROM THE IMMEDIATE ROOF, HIT THE ROOF BOLTER CANOPY AND BROKE IN TO SMALLER PIECE A TRIANGULAR STOPPED PEKE 24"" AT BASE 18"" HEIGHT 1 1/2"" THICK CAROMED OFF THE CANOPY STRIKING EE ON HIS BACK. WITH NO APPARENT BRUISES HE FINISHED BOLTING. BUT THEN HE COMPLAINED OF BACK PAIN AND WAS TAKEN OUT OF MINE AT APP