In their work, the authors study what it looks like to build on a high-leverage student mathematical contribution--one that provides an in-the-moment opportunity to engage the class in joint sense making about the contribution to better understand the important mathematics within it. They have noticed that some "go-to" teacher practices work well in some situations but can actually be counterproductive in others. In this article, the authors discuss three of these practices that they have seen regularly: (1) collecting information from the class; (2) asking a student to clarify their contribution; and (3) asking students to revoice a peer's contribution, providing examples of both productive and counterproductive uses of each practice. Understanding these distinctions helps teachers become more intentional about the practices that they engage in to facilitate whole-class discussion that builds on students' contributions. To illuminate the distinctions, the authors use excerpts based on classroom discussions in video recordings provided by middle and high school teachers as part of a research project. Although the project has been based in secondary classrooms, the practices occur at all levels. The end of the article includes a video where the authors discuss these ideas within an elementary school classroom episode.