We are a small intermodal depot for empty containers. As do many other depots in our city, we stack containers 2 - 3 high for empty storage. Recently there was a wind storm which blew a container into a neighboring business parking lot. While there was minimal damage and no one was injured...the question was raised...is there a manufacturers regulation or suggestion as to how high empty containers should be stacked without locking mechanisms? Could you possibly offer any documentation which would clear up this issue?