How do practitioners—of any form of specialized knowledge—learn technical skills, and how do they find knowledge deemed solid and secure? Clearly, much training occurs within formal situations such as schools and laboratories. Classrooms and their textbooks have attracted due attention from historians, with a focus in the last decade or so on how teachers convey working knowledge bodily and not only abstractly to their students or apprentices. But learning does not stop with formal education, and often enough it starts elsewhere. Manuals and handbooks have long enabled informal, often self-directed education and training. They also provide a new vantage point for bringing together history of science with history of books and media, from antiquity to the present. These instructional texts and compendia codify the knowledge of a working community with an eye to communicating what a new practitioner needs to know. Such texts have also played a key role in bringing local knowledge and know-how to far-flung readers and practitioners around the globe. By following these apparently mundane texts and their uses, rather than focusing only on elite practitioners, we bring into view an exciting new set of historical connections and participants.