EE WAS HELPING ANOTHER EE DISMANTLE AN OVERCAST WHICH HAD BEEN TAKEN OUT OF SERVICE. THEY WERE REMOVING THE LAST SIDE SECTIONS OF TIN WITH SLEDGEHAMMERS WHEN THE OVERCAST SUPPORT BEAMS SHIFTED AND FELL, STRIKING EE ON THE SHOULDER AND BACK OF THE HEAD. THIS RESULTED IN A LACERATION TO THE BACK OF HIS HEAD.