Single Display Groupware (SDG) lets multiple co-located people, each with their own input device, interact simultaneously over a single communal display. While SDG is beneficial, there is risk of interference: when two people are interacting in close proximity, one person can raise an interface component (such as a menu, dialog box, or movable palette) over another person's working area, thus obscuring and hindering the other's actions. Consequently, researchers have developed special purpose interaction components to mitigate interference techniques. Yet is interference common in practice? If not, then SDG versions of conventional interface components could prove more suitable. We hypothesize that collaborators spatially separate their activities to the extent that they partition their workspace into distinct areas when working on particular tasks, thus reducing the potential for interference. We tested this hypothesis by observing co-located people performing a set of collaborative drawing exercises in an SDG workspace, where we paid particular attention to the locations of their simultaneous interactions. We saw that spatial separation and partitioning occurred consistently and naturally across all participants, rarely requiring any verbal negotiation. Particular divisions of the space varied, influenced by seating position and task semantics. These results suggest that people naturally avoid interfering with one another by spatially separating their actions. This has design implications for SDG interaction techniques, especially in how conventional widgets can be adapted to an SDG setting.