from the Window Sox website...
Under "About Us": "Window SOX® are a new effective product for providing shade and insect protection when placed on the rear windows of your vehicle."
So in black and white, Chazz has the right of it. I am looking for just such a product, and remembered this description from my search.
He is also correct about lawsuits, because "There is no such thing as a foolproof system, since fools are so damn clever." I may add, they also seem to gravitate to lawyers, and lawyers only exist because of human folly. I am not being cynical; think about it.