A simple double accordion structure requiring no sewing or glue. Two accordions are folded, a V shape is cut from one, then a wedge is cut [using the width of the V as a measurement] from the folds to the outside corner on the other. The wedge is rolled to slide thru the V. That's it. This would be best made as an eight-panel folded accordion, although the model shown is four panels. Love the light and shadow play!