HANGABLE FREE-FORM SKEEWBACKERSTM
Hangable Skeewbacker Free-Form Shapes are designed to have a hanging system installed directly to the backer. One is available or you can make your own. Each is 12" on the long dimension and there are 17 shapes to choose from. They are constructed from a rigid polystyrene foam core sandwiched between waterproof membranes.
see this short video on installing the hanging kit