The concept that technology should be designed iteratively is a well-established tenet in participatory design. However, iteration has received insufficient attention regarding how and why we should also evolve tools that support participatory processes. Based on empirical material from five participatory renewable energy projects conducted in different school communities, this paper documents how a seemingly mundane participatory design tool, a paper template, evolves through iteration to better scaffold collaborative design work. We show how iteration has implications for the overall direction of the project towards sustainability by surfacing future issues. The templates allowed a collective move from designing a renewable energy generator towards making a school collective for sustainable use, management, and adjustment of the generator they built. The iterations illustrate how participatory design tools can collect mundane things relevant for design decisions and how such things can be translated at higher levels.