What does it mean to use something from a design point of view? As an alternative to role-based accounts of designers and users, this paper presents an act-based account that centres on what it is we do rather than who we are. More specifically, the paper analyses relations between design and use with focus on how open a design (process) is with respect to definitions of use through use; from well-defined influence from specific user tests on design decisions, via extensive user participation in the design process, to open-ended design processes that extends into what we otherwise understand as use. Thus, it transforms the relation between design and use into a question not of who, but of how.