Most libraries around the world use the Dewey Decimal Classification System (DDCS) to list and categorize books. The DDCS is a library classification system developed by Melvil Dewey in 1876. By categorizing items within a library it serves as a tool for people searching for specific knowledge. It was an attempt to organize all knowledge into ten main classes, which are further subdivided into 100 divisions and 1000 sections. This makes the DDCS appear purely numerical and infinitely rational. However, DDCS is regularly revised, reflecting how culture, ideology, and the perception of knowledge change over time. As a result of these changes and to provide for future alterations 89 of the 1000 sections in the system are classified as " Unassigned."For this issue of Shifter we invited artists, writers, activists and scholars to comment on, disturb and restructure the logic of this system by adding new categories to fill the unassigned spaces. These comments, reflections, parasite systems or prosthetic extensions all expand on what is structurally "knowable" within the institution of the public library, by opening up the possibilities held within its undefined categories.Contributions by Avi Alpert, Kim Asbury, Lindsay Benedict, Karlotta Blöndal, Emil Madsen Brandt, Dion Farquhar, Alison Gerber, Joshua Hart, Jesal Kapadia, Philipp Kleinmichel, Yahia Lababidi, Lawrence Liang, Karl Lydén, George Monteleone, Huong Ngo, Morgan O'Hara, Annika Ruth Persson, Jean-Marc Superville Sovak, Adam Trowbridge, Anna Vitale, Ylva Westerlund