Multi-device product designers need tools to better address ecologically valid constraints in naturalistic settings early in their design process. To address this need, we created a reusable design kit of scenarios, “hint” cards, and a framework that codifies insights from prior work and our own field study. We named the kit the Moving Context Kit, or McKit for short, because it helps designers focus on context shifts that we found to be highly influential in everyday multi-device use. Specifically, we distilled the following findings from our field study in the McKit: (1) devices are typically specialized into one of six roles during parallel use—notifier, broadcaster, collector, gamer, remote, and hub, and (2) device roles are influenced by context shifts between private and shared situations. Through a workshop, we validated that the McKit enables designers to engage with complex user needs, situations, and relationships when incorporating novel multi-device techniques into the products they envision.