This article discusses a case study of a pair of students mentored by a physics teacher as they engaged in a long-term (15 months) engineering maker-based inquiry (EMBI), a mandatory part of these students' formal learning of physics at the advanced high school level. We conceptualize the students' engagement as participating in a particular figured world, which is distinct from the figured world of authentic scientific inquiry. Using fine-grained discourse analysis of mentor-mentee interactions in authentic working sessions, complemented by interviews and other ethnographic accounts, we: (a) characterize this figured world; (b) identify central legitimate forms of participation that were enacted by the students and influenced their learning; (c) articulate how these forms of participation were socially communicated, constructed, and enforced over time in the interaction between the two students and the educational staff; and (d) examine how these forms of participation facilitated (or impaired) the learning of content and practices of the related physics. Two legitimate forms of participation, which contributed extensively to the EMBI's goal of creating a working artifact, are discussed in detail. The analysis articulates the social construction of these forms of participation and shows that (a) "participating as an engineer" facilitated many foundational aspects of learning of physics, (b) "participating as a technician" fostered a sense of agency and efficacy with regard to physics in a student who did not find ways to express himself in the regular physics classroom; however, it did not facilitate the learning of scientific content and practices. The implications for the instruction of physics in school, particularly given recent calls for integrated STEM education and Making in education, are discussed.