Research has rarely taken into account the role of the written production of teachers in the process of teaching. Although, some of Nonnon’s work (1991, 2000) in French didactics and Robert & Vanderbroucke (2003) in the didactics of mathematics have shown the importance of this production, developing the example of the black board.

This practice (writing on the board) is said by the teachers to be fundamental and very frequent, but paradoxically enough, it is little known and theorised.

Following Borzeix and Fraenkel’s work (2001) in the field of the “language and work”, this article is an attempt to probe writing on the board as a professional practice in the sense that it allows teachers to fulfil their work, that is “teach and make learn” (Tardif & Lessard, 1999), even if it is not fully mastered.

In a didactic perspective, the article explores the functions and forms of this practice as both a language and a professional practice in order to highlight some of it disciplinary specificities. These two issues will be addressed on the basis of classroom observations and interviews conducted with teachers from elementary and secondary schools.