A policy consensus has emerged in Australia that there is a workforce literacy and numeracy crisis, similar to many other Organisation for Economic Cooperation and Development countries. The study informing this paper examined this framing of crisis by interviewing and observing production workers in three manufacturing companies. Each company was implementing new lean production methods, known as "competitive systems and practices", based on a visual workplace management system. In this paper, we look at what is visible and invisible in production workers' literacy and numeracy practices at Hearing Solutions, one of the companies in the study. We begin by considering the overarching policy discourse around workers' literacy and numeracy before exploring the underpinning rationale of the new expression of lean manufacturing, in particular, its implementation through the Visual Workplace Management System. Detailing an example of the literacies used in producing hearing aid shells, we discuss the under-valuing by workers and managers of the skills being used; and the hidden process of industrial relations, reward and remuneration. Using an ethnographic and social practices approach, what emerges is a better understanding of the complex range of vocational knowledge and social skills being used that go unrecognised by policy makers, lobbyists and managers, and even by the workers themselves.