THE EMPLOYEE FINISHED BOLTING A CUT AND WAS CLEANING HIS DUCT BOX. HE FELT THAT HIS METACARPAL GLOVES WERE NOT NEEDED FOR THE TASK. AFTER CLEANING HIS DUCT BOX. HE GRABBED THE TOP OF THE BOLT MACHINE TO HELP HIMSELF UP FROM A SQUATTED POSITION. AT THIS TIME A ROCK 2 IN THICK BY 12 IN WIDE FELL FROM BETWEEN THE BOLTS AND LANDED ON HIS RIGHT HAND.