Facilitating productive mathematical discussions is considered a core practice of mathematics education. The complexity of this teaching practice presents the need for pedagogical tools to provide structure for preservice teachers (PST) developing their practice, yet little is known about "how" PSTs use these tools. This multiple case study sought to understand what pedagogical tools PSTs use to plan and enact mathematical discussions with elementary students and how they use these tools to support their practice. In particular, this study focused on capturing the experiences of three elementary PSTs as they transitioned from university-based methods course instructions into early clinical teaching experiences in elementary classrooms. These experiences were captured through multiple one-on-one interviews, observations of teaching in clinical classroom settings, and analysis of artifacts of teaching and learning. This study has implications for mathematics teacher education, practice-based teacher education, and the refinement of tools to support teachers' practice facilitating mathematical discussions with students. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]