THE INJURED WHO IS A ROOF BOLTER, WAS ON HIS KNEES HANGING LINE CURTAIN, OUT OF SIGHT OF THE OTHER PERSON WHO WAS BOLTING ROOF. AS THE OTHER ROOF BOLTER MOVED THE ROOF BOLTING AHEAD TO INSTALL A BOLT, HE INADVERTENTLY RAN THE WHEEL OF THE BOLTING MACHINE ON THE FOOT OF THE INJURED PERSON.