WHILE INSTALLING CHAIN HANGERS, THEY WERE ADVANCING THE ROOF BOLTER THRU A BLOCK CURTAIN WHEN ONE OF THE DRILL STEELS GOT CAUGHT IN THE CURTAIN. EE WENT TO THE FRONT OF THE ROOF BOLTER TO PULL THE STEEL OUT OF THE CURTAIN AND WHEN HE RAISED THE CURTAIN THE DRILL STEEL CAME LOOSE AND HIT HIM IN THE MOUTH.