An employee was trying to remove and re-stack cases from a pallet that had turned over on the fourth level of a storage rack in a freezer. He placed two empty pallets in the rack, one to stand on and one to stack product cases on. He climbed up the end cap and onto one of the empty pallets. The turned-over pallet of product shifted, knocking the empty pallet through the racking. The employee fell approximately 20 feet from the fourth level and sustained a neck fracture.