Reflection is a common activity at work. Collaborative reflection is an activity in which multiple participants add to reflection by sharing experiences, perspectives and insights together, thus transcending individual capabilities. Despite its potential for change at workplaces, there are little insights on how to support collaborative reflection with technology. To close this gap, this paper analyses four cases in which a tool to support collaborative reflection has been used at different workplaces. It uses qualitative data from app usage, an analysis of content from the tool and feedback gathered from participants to shed light on how people use support tools for collaborative reflection. The results of this wok include factors supporting and constraining reflection in tools as well as implications for tool design.