The materials and artefacts used by teachers and students for learning mathematics have always had an important role in mathematics education. Key among such materials are textbooks and teacher guides. The study presented in this paper attempts to investigate the interaction between mathematics teachers and the teacher guide as well as its influence on textbook use in the classroom. The qualitative approach involved a case study with two mathematics teachers from Croatia. The results showed that the participants used different types of textbook and teacher guide mobilisation in a dynamic way. The analysis of the teacher guide showed that it contains little educative support, but the results obtained from the observations and interviews suggest that the teacher guide had an educative impact on teachers, supporting their use of active teaching methods in their classroom practice.