This study aims at exploring forms of mediation occurring when social mediators (SM) offer assistance to migrants and help them access social, legal and healthcare services. One recurrent activity in this context is the understanding/explanation of procedures (for carrying out an administrative procedure, obtaining civil or legal rights, etc.). This type of activities may encompass several forms of mediation. First, the delivery of information regarding the type of documents or procedures required accessing a required official service. Second, the reading and oral reformulation of written documents the migrants hold. Third, the oral translation of talk, provided by a lay interpreter when participants do not speak a common language. Participants are thus called to construct an understanding of the required service, and of the procedure needed. These are built by putting together the information offered by the layperson, the information found in the documents, and the SM and interpreter’s own knowledge and experience in dealing with a procedure or issue. The analysis will specifically focus on the organization of participation and on the use of the users’ documents, which become the object of a close inquiry. It will show in detail that the understanding of the documents’ content and of the procedure, and their explanation to the user is not a one-way process but rather a complex and multidirectional enterprise. In this sense, the interpreter’s activity is oriented to co-occurring activities. We use conversation analysis and multimodal interaction analysis as methodological framework to analyse our data, drawn from a corpus of video-recorded encounters at a French social center.