A rattleback is a well-known physics toy that has a preferred direction of rotation. If it is spun about a vertical axis in the "wrong" direction, it will slow down, start rocking from end to end, and then spin in the opposite (i.e. preferred) direction. Many articles have been written about rattlebacks. Some are highly mathematical and others are purely descriptive. It is surprising that there is still no simple physical explanation that can be given to a high school student and one that does not involve an obscure set of complicated equations.