The opening essay of this chapter, "From Dirty Marks to Lines, Shapes & Representations" first confronts the difference between a mark and a line. A mark is literal, direct, and unambiguous in its creation. In the previous chapter, exercises prompted the codification of marks, but in some cases, the marks were not lines. This is not a matter of nomenclature, extremity or classification. No matter how bombastic, trail-like, curvy or straight the mark, it might not always register as a line. This is because lines are relational mental constructs. A line is what we read into marks. Sometimes, the association between marks and lines is not one to one. Consider two marks made by a pen in exactly the same location. Consider 100 such marks. The line read by those marks may be different depending on the number of marks, but it is still only one line. Consider the horizon line. The horizon line is real; it can be measured, photographed, described, and defined, but it is not a thing. It can be perceived without association with a single mark. A mark does not always lead to a line and a line is not always made up of one mark. Consider, further, that a line can exist because of the tension between marks—as in when our mind literally connects the dots—or a complete lack of marks—as in when marks fill an area to maximum density except for a small sliver of space. This chapter continues in pursuit of drawing structures with an inquiry into various taxonomies of line. Throughout this taxonomy of taxonomies exercises and algorithms push the scope of coding into the space of line behavior, relationship and evaluation.