In the present paper, I address the writing practices, more specifically, the use of projective narratives and self-observations (Bombini, 2012) in the initial training of language and literature teachers. However, the treatment of this topic is not the main objective of this presentation. I am interested in focusing on didactic research on training devices and in differentiating (and why not, defining) this type of research as opposed to those carried out by other areas. The study of projective narratives and self-observations is the point of argumentation that allows me to demonstrate how scientific activity in the field of didactics contributes to the construction of knowledge that makes it possible to transform and generate new teaching and learning practices in the classroom. Unlike the interests of other disciplines, didactic research has the capacity to offer an explanation and a joint and coherent understanding of the relationships between the processes of treatment and transformation of information into knowledge, the teaching process and the didactic engineering that this provokes and the learning process by the students. Through the exposition of a study on training devices, we will observe how the interest in these teaching instruments offers a gateway to explain and understand the didactic system of teaching practices in initial training.