In this study, we examined maker-centred learning from an epistemic perspective, highlighting the agentic role of material engagement and artefacts in learning and creativity. The use of physical materials plays a crucial role in maker activities where the socio-epistemic aspects of knowledge creation entangle with the designing and making of physical artefacts. By taking a case study perspective, we analysed video data from nine design sessions involving a team of students (aged 13 to 14) developing an invention. First, we analysed knowledge that was built during the process. Our analysis revealed how design ideas evolved from preliminary to final stages and, together with the expressed design problems and conversations preceding the ideas, formed an epistemic object pursued by the team. Next, we included non-human agencies into the analysis to understand the role of materials in the process. Features of materials and human design intentions both constrained and enabled idea improvement and knowledge creation, intermixing meanings and materials. Material making invited the students to not only rely on human rationalisation, but also to think together with the materials.