Marble is cut by slabs of stone. If you take two consecutive slabs and flip them you get a mirror image. There is one roll of marble wallpaper (f.e. PHM-51A), and another roll thatâ€™s the mirror image of it (f.e. PHM-51B). These two rolls combined give the impression of an opened book. In marble this is called â€œbookmatchâ€. Piet Hein Eek, "A lot of companies have made marble reproductions products, but never in the way we envisioned it."