PERSON HAD FINISHED DRILLING HOLE IN ROOF TO INSTALL BOLT. PERSON LOWERED BOLTER HEAD AND REACH OUT TO REMOVE DRILL STEEL EXTENSION. THE TOP PART OF DRILL STEEL WHICH WAS BEING HELD BY DRILL S TEEL GUIDE JAWS, SLIP DOWN THROUGH DRILL STEEL GUIDE AND STRUCK PERSON ON MIDDLE FINGER OF LEFT HAND CAUSING LACERATION AND DAMAGE TO TENDON.