Paleontology laboratories are crucial sites of specimen production and therefore knowledge production for fossil-based research. However, the work and workers of these labs are rarely described in publications, or even in lab records. The processing of fossils into specimens is called fossil preparation and is primarily done by fossil preparators, who learn their skills on-the-job. Preparation involves removal of rock matrix and repair and reconstruction of fossils, but techniques are diverse, often adapted, and largely unrecorded. Steven Shapin argues that omitting workers, such as technicians, from research reports makes them and their practices “invisible” – unknown and unrecognized. Considering why preparators and their work are “invisible” in scientific publications reveals the implicit foundations of both practice and social order in scientific workplaces. To investigate the invisible people and unwritten practices of fossil preparation, I interviewed, observed, and collected survey responses from workers in paleontology laboratories in the United States and the United Kingdom. These data reveal how scientific work depends on nonstandard practices and informally-trained people. Unlike studies that point to benefits for researchers of the invisibility of laboratory work and workers – i.e., to make knowledge claims appear more credible – this case suggests benefits for technicians of being overlooked, namely the preservation of workers’ power over their practices. Science can thus be understood as work done by a community – locally contingent and crucially based on conceptions of skill and status.