PRIOR TO MOVING TO THE NEXT PLACE TO BOLT THE OPERATOR & HELPER SHUT DOWN AND TALKED. THE OPERATOR STARTED THE MACHINE UP & DROPPED THE ATRS NOT KNOWING THE HELPER SAW HIS BOLT MEASURING ROD A GAINST THE FACE. WHEN THE T-BAR WAS RELEASED IT HIT THE HELPER IN THE LEFT BACK & SHOULDER AREA KNOCKING HIM FROM A CRAWLING TO A PRONE POSITION.