EE WAS OPERATING THE TRAIL LOCOMOTIVE IN A TRIP OF CARS. ROOF BOLTS THAT WERE IN THE SUPPLY CAR CAUGHT THE ROOF AND CAME BACK STRIKING HIM IN THE SHOULDER. CAUSE OF THIS INJURY WAS HEIGHT OF SUPPLIES VERSES THE ROOF HEIGHT. COMPLIANCE WITH RULES/REGS NOT A FACTOR; PROCTECTIVE EQUIPMENT NOT A FACTOR; MINER KNOWLEDGE COULD BE A FACTOR; MINING EQUIPMENT/SYSTEMS COULD BE A FACTOR.