First, you fold your paper in half and press along the line. Next, you're going to cut along that line with a pair of scissors. Next, the artist uses a ruler to mark a three-centimeter line and glues the two pieces of paper together, lining up the marks. Fold this in half, pressing the fold carefully, and then press those towards the centre, creating four segments. You can then concertina-fold your sketchbook and it is complete.