INSTALLING ROADWAY REFLECTIVE UNITS ALONG THE MOUTH OF JARRELL'S BRANCH BETWEEN THE TRACK RAIL CROSSING & THE POND. EE WAS DRIVING THE UNIT REFLECTOR INTO THE GROUND WITH A HAMMER. HAMMER MISSED THE POST, CAUSING EE TO MASH HIS RIGHT FINGER ON THE TOP OF THE UNIT POST. MEDICAL REPORTABLE ACCIDENT; EE RECD. 4 SUTURES AT A MED. FACILITY. EE DID NOT MISS ANY WORK.