Mechanic was trying to free the end of the hard bar that had dropped down and wedged into the roller frame. They were using a hyd. jack to push the roller frame out placing crib block under the bar when it came free from it's position as EE was placing a crib block under it and the roller frame shifted inward striking mechanic on the head on EE's hard hat causing a cervical strain
U.S. Mine Safety and Health Administration