Cyperus papyrus
Papyrus is prepared by cutting off thin ribbon-like strips of the interior of the "Cyperus papyrus", and then laying out the strips side-by-side to make a sheet. A second layer is then placed on top, with the strips running at right angle to the first. The two layers are then pounded together into a sheet. The result is very strong, but has an uneven surface, especially at the edges of the strips. When used in scrolls, repeated rolling and unrolling causes the strips to come apart again, typically along vertical lines. This effect can be seen in many ancient papyrus documents.