One SHEET of TRU-Flat® paper spreads from the far left side of the open book to the far right side of the open book. There is no gutter or binding in the spine area. We refer to this entire spread as one SHEET since only one sheet of TRU-Flat® paper is used. Old book binding terms would consider this a two-page spread or two PAGES of the book. This is probably the most confusing new concept to learn when working with the new TRU-Flat® technology, but it makes page layout a snap.