THE FRONT END OF WATER TRUCK HAD BEEN JACKED UP AND CRIBBED WITH 6"" CRIB BLOCKS IN ORDER TO REBUILD BRAKES. EE INSPECTED THE AREA BEFORE REMOVING THE WHEELS AND DECIDED TO REPOSITION THE CRIBS . HE JACKED THE TRUCK UP, REPOSITIONED THE CRIBSLIKE HE WANTED AND AS HE REACHED OVER TO PULL THE HANDLE OUT OF THE JACK THE 20 TON JACK SLIPPED OUT AND STRUCK HIM IN THE HEAD (BROW).