WE WERE USING A CRIB BLOCK TO BLOCK OPEN THE TAILGATE OF A MACK MUD TRUCK SO WE COULD CLEAN MUD FROM AROUND TAILGATE, AS WE WERE PLACING CRIB BLOCK AGAINST TAILGATE, CRIB BLOCK SLIPPED & STRUCK THE RIGHT WRIST OF INJURED EMPLOYEE. HE DID NOT WANT TO SEE A DR. AT THAT TIME BUT LATER ON THE 24TH HE WENT TO A DR.