rotulus

thumb|Volumen and Rotulus

A rotulus (plural rotuli) or rotula (pl. rotulae), often referred to as a "vertical roll," is a long and narrow strip of writing material, historically papyrus or parchment, that is wound around a wooden axle or rod. Rotuli are unwound vertically so that the writing runs parallel to the rod, unlike the other kind of roll, called a scroll, whose writing runs perpendicular to the rod in multiple columns.