Following citation trails, or citation tracking, is a technique taught by librarians for finding scholarly literature, and of following ideas or arguments over time. As a supplement to keyword searching, it is an important component in library education for students writing a literature review. The practice of following citation trails has been transformed by citation counts in large citation indexes, and academic search engines such as Google Scholar. On university library websites, citation tracking is often presented as a neutral tool for finding and making sense of literature. High numbers of citations are often linked to the assumed quality of a published text, and these claims are reinforced on the websites of the large platforms which produce these tools. Despite librarians’ role teaching students about citation counts and citation tracking, limited attention has been paid to this teaching. Emerging debates within scholarly literature suggest that tools such as citation counts are not neutral and instead posits them as performative practices. My research adds to this conversation by exploring the ways in which librarians are implicated in the framing of understandings of the production of knowledge in their teaching. In this presentation, I think with Karen Barad’s notion of apparatus, as well as Sara Ahmed’s notion of use, to explore the performative nature of citation counts and citation trails. The presentation is based on a pedagogical encounter in which a liaison librarian teaches an Education Master’s student how to use Google Scholar’s “Cited by” feature, a citation count of a published text, hyperlinked to a list of works citing that text. Within the intra-activity of the pedagogical encounter, bodies and boundaries are emergent and shifting. Citation counts, which measure academic standing, materialise the student and her topic as mattering less. Within this mattering, librarian professional expertise emerges, entangled with the exclusion of the student, understandings of knowledge, and also the infrastructure of the platform university. This data is part of a PhD project which used a diffractive approach to explore the mutual constitution of librarian professional expertise, spaces and technologies within pedagogical encounters.