Introduction One key aspect of our teaching profession is to understand the relationship between the instructor and the teaching materials. Teaching materials are ubiquitous in teaching and learning in general, including teaching and learning a second language (L2). Materials are seen as tools that mediate teaching and learning and play a key role in facilitating the teaching and learning process. How teachers use materials has become relatively recently a focus of materials research, along with the other two aspects of this area which have received more attention in the past, such as materials development and materials evaluation (Gray, 2012; Tomlinson, 2012). The purpose of this chapter is to contribute to our understanding of how teachers use materials in the classroom within a task-based curriculum. Another aspect to understand when we talk about materials use is the difference between the written materials (also known as written curriculum or institutional curriculum) and the enacted materials (or enacted curriculum) (Graves, 2021). Written materials, such as textbooks, are developed with particu- lar learning and teaching objectives, with a lesser or greater knowledge of who the potential users (i.e. teachers and learners) may be, and with or without a clear intention of how they may be used. Enacted materials, on the other hand, are the written materials that become transformed into real teach- ing experiences through teachers’ engagement and interacting with these resources (Remillard, 2005). Lloyd et al. (2008) explain that materials use is a variety of interrelated pedagogical activities and involves substantial engagement, interpretation and decision-making on the part of the teacher. Another aspect important to understand in materials use is that teachers are key agents in materials use and they, consciously or unconsciously, adapt their materials to a lesser or greater degree by the mere act of using them. There exists the wrong assumption that the way teachers teach is uniform, that teachers are mere conduits of the written curriculum, and the way the learners learn is predicta- ble (Graves, 2021). By the same token, materials are used differently by the same teachers in different contexts, and teachers using the same material in the same context will use it differently (Menkabu and Harwood, 2014). Even if the intention were not to change materials at all, given the constellation of How are materials actually used? Instructor’s task enactment in L2 Spanish in higher education Claudia R. Fernández Chapter 3 9781350199675_txt_rev.indd 73 02-03-2023 16:55:04