In public health emergency preparedness and response (PHEP), plans are a central matter of concern. Understanding plans' role in establishing, facilitating, or securing preparedness and response objectives is of enduring practical and theoretical warrant. Drawing from practice-based perspectives and treating plans as sociotechnical objects, this project aims to describe ways in which theoretical approaches to plans shape their use, meaning, and value in actual practice. Employing empirically-grounded and interpretative methods, it investigates divergent accounts of plans' role for the purpose of identifying assumptions about the mechanisms by which plans' achieve their practical effects. The consequences of these assumptions on how plans are written and used are explored in separate case studies. The first focuses on the modalities for coordinating functional response activities within local health departments' preparedness and response plans in the U.S. The second focuses on the modalities for coordinating information globally within the International Health Regulations (2005). Both cases demonstrate that the capacities of plans to realize functional or operational objectives i.e., the mechanisms of how plans work, depend on the dominant theoretical approaches in the relevant setting.