Shared understanding plays a key role within the emergency-planning context to successfully develop planning tasks. Particularly in ‘tabletop’ exercises, such an understanding is required to make decisions about planning. However, as the task progresses, the amount of relevant knowledge that a planner can remember about the task progressively decreases. This fact can impose a limit on the task progress. With the purpose of overcoming such a limitation, this work presents a computer-based face-to-face collaborative tool aimed at supporting ‘tabletop’ exercises.