EE REPORTED: HELPING COWORKERS PLACE EXPLOSIVES ON LARGE ROCKS IN FRONT OF SHIELDS AT TAILGATE AREA OF LONGWALL FACE LINE. HE WAS STANDING UNDER SHIELDS NO. 136 & 137 WHEN A SMALL PIECE OF ROC K FELL FROM BETWEEN THE TWO SHIELDS. THE ROCK STRUCK THE BACK OF HIS HEAD JUST UNDER HIS PROTECTIVE MINE CAP RESULTING IN A SMALL LACERATION AND A MILD CONCUSSION.