This mixed-methods study probed the effectiveness of three kinds of objects (video, theory, metaphor) as common reference points for conversations between online learners (student teachers). Individuals' degree of detail-focus was examined as a potentially interacting covariate and the outcome measure was learners' level of tacit knowledge related to their practice (teaching). Analysis was conducted using hierarchical linear modeling and significant results were followed up with a qualitative theme analysis. An interaction between reference point type and detail-focus was found, demonstrating a positive effect of detail-focus within the metaphor condition. Unexpectedly, some participants interpreted the metaphors in ways other than those intended, leading to differences in the kinds of understandings developed. The study indicated that a conceptual frame is an important characteristic of a reference point that will be truly taken in common, and that metaphors need additional framing to be viable in this role. Implications for online learning conversation design are discussed. (Contains 2 figures and 4 tables.)