Unlike our notebooks today, medieval paper and parchment sheets did not come with ruled lines when you purchased them. A medieval page consisted of both horizontal and vertical ruling. To add these guiding lines to the blank page, the scribe would prick tiny holes in the outer margins, as well as in the upper and lower ones. Lines were then drawn between these holes, usually with the help of a ruler: horizontal lines to guide the space between each line of text, and vertical lines to confine the left and right side of the textblock.
Until the early twelfth century the ruling was done by pressing down on the parchment with a sharp object, producing a "gutter" that would guide the scribe’s pen (called ‘dry point’). This type of ruling was replaced by drawing lines with a pencil or pen, which left more visible traces on the surface of the page (called 'plummet'). If a layout was very complex, the ruling pattern may appear as a cobweb of horizontal and vertical lines.