An employee and a backhoe operator were leveling the waler on a slide rail system. The backhoe operator flipped the bucket, pushed up the waler, and lost sight contact with the employee. The operator then lost his grip on the bucket, causing the waler to fall. The waler hit a 8' 2"x4" piece of wood, which jumped up and hit the employee in the face. The injured employee lost consciousness and was hospitalized with a fractured jaw.