EMPLOYEE LAID HIS IMPACT WRENCH WHICH HE WAS PLANNING TO USE TO TIGHTEN BOLTS ON THE LID ONE HE CLOSED THE LID ON THE TANK CAR. HOWEVER, WHEN HE CLOSED THE LID WITH HIS LEFT HAND, HIS LEFT LIT TLE FINGER WAS CAUGHT BETWEEN THE LID AND IMPACT WRENCH. HE SUSTAINED A LACERATION AND FRACTURE OF HIS FINGER.