Rules are one way of attempting to manage or minimize conflicts within activity systems-including conflicts and problems related to tool use, division of labor, and motives. Rules are defined not only as formal and explicit dos and don'ts, but also as norms, conventions, and values. "Rules shape the interactions of subject and tools with the object" (Russell, 2002). Rules understandably change as other aspects of the system change-or as the rules are questioned or resisted-but the rules allow the system to be stabilized-for-now (Schryer) in the face of internal contradictions.