Not all lines on maps are made by a cartographer. When maps are repeatedly folded and unfolded and stuffed into pockets on trips, they develop another grid of lines just as enduring as those in ink. Evidence of these lines of use reminds us that maps are more than just objective representations of facts but viewpoints into different understandings of place that carry their own imperfections and histories. For contemporary artists, these inkless lines evoke the unwritten rules that have shaped heavily segregated cities like Chicago and Detroit. Redlining, a term that refers to policies of race-based housing discrimination in US cities, is rarely visible as a bright line on a map. Like lines from folds, lines of segregation and discrimination instead only become visible when we understand how people actually live in these cities.