What kinds of curriculum materials do mathematics teachers select and use, and how? This question is complex, in a period of deep evolutions of teaching resources, with the proficiency of online resources in particular. How do teachers learn from these materials, and in which ways do they `tailor' them for their use and pupil learning? Teachers collect resources, select, transform, share, implement, and revise them. Drawing from the French term " ingenierie documentaire ",we call these processes " documentation ". The literal English translation is " to work with documents ", but the meaning it carries is richer. Documentation refers to the complex and interactive ways that teachers work with resources; in-class and out-of-class, individually, but also collectively.