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-41A), and another roll that’s the mirror image of it (f.e. PHM-41B). These two rolls combined give the impression of an opened book. In marble this is called “bookmatch”. You can create a wall as shown on images 3 (mirrored strips) ordering a regular roll (PHM-41A) and a mirrored roll (PHM-41B). Piet Hein Eek, "A lot of companies have made marble reproductions products, but never in the way we envisioned it."