Online C to C platforms rely on multiple evaluation tools (ratings, calculated reputation, and online reviews) to generate the trust that is essential for transactions. What are the sources of trust when these tools are absent (or not used)? From an ethnography of private transactions via leboncoin.fr, this contribution reveals the mechanisms of trust in this context. The Goffmanian approach adopted enables us to highlight the rules of trust and their role in maintaining and repairing trust situations (commitment, normality, proximity, readability, and unveiling). This research contributes to the marketing literature by supplementing the work on the evaluative and calculated character of trust and by proposing a cross-channel analysis incorporating online trust. It opens up alternative perspectives for framing C to C exchanges and studying cross-channel consumer behavior.