Information transformation is key to engineering design work. However, research on how information management tools, and logbooks in particular, mediate this, is fragmented. We explore this via two studies (from which we confirm the central role of logbooks) and propose three modes of mediation: facilitating cognition and creation, gathering and collation of information, and staging and transformation of information. The findings explain the widespread use of logbooks through their support of these three modes. Consequently, we contend that multi-modal mediation is one of the main reasons why logbooks are such a central and enduring medium. This synthesises and extends theory on mediation and information use in engineering design. Further, practical insights are derived for the development new information management tools.