Mature eXtreme programming (XP) teams are highly collaborative and selforganising. In previous studies, we have observed that these teams rely on two apparently simple mechanisms of co-ordination and collaboration: story cards and the Wall. Story cards capture and embody the user stories which form the basis of implementation, while the Wall is a physical space used to organise and display the cards being implemented during the current development cycle (called an iteration). In this paper we analyse the structure and use of story cards and the Wall in three mature XP teams, using a distributed cognition approach. The teams work in different commercial organisations developing different systems, yet we find significant similarities between their use of these two artefacts. Although simple, teams use the cards and the Wall in sophisticated ways to represent and communicate information that is vital to support their activities. We discuss the significance of the physical medium for the story cards and the Wall in an XP team and discuss the considerations that need to be taken into account for the design of technology to support the teams
