Materials use is a critical yet poorly understood dynamic of language classrooms. This study examines 'materials-in-action,' meaning how materials shape classroom interaction and activity, in a beginning-level French-as-a-foreign-language classroom. The conceptual framework, 'pedagogical ergonomics,' similarly centers on materials-in-action, and more specifically on 'intra-action.' This refers to actions, influences, engagements, and exchanges among (a) materials, and (b) the students and teacher. Polysemiotic analyses and action analyses of classroom activity were triangulated with interviews and focus groups. Findings first expound the pedagogical ergonomics framework as comprising intra-actions among human and material 'actants' that are co-substantiated with sociocultural and physical space. This involves the concept of 'classroomscape.' Then--drawing on pedagogical ergonomics--macro-level analyses of materials-in-action reveal 4 genres of materials use, each of which influenced classroom activity and interaction differently. Additionally, micro-level analysis reveals 3 polysemiotic patterns of materials-in-action: (a) cloze worksheet prompts that 'mapped' onto the students, (b) learners' 'snowball languaging' in French--involving extended meaning-focused descriptions of images--and (c) a physically dynamic information gap where students unexpectedly avoided using French. Additionally, this article hones the definition of 'materials use,' substantively focusing on activity and interaction. Theory and practice converge in pedagogical ergonomics, with implications for both.