This article takes the reader inside four border security fairs in Europe and North America to examine the knowledge practices of border security professionals. Building on the border security as practice research agenda, the analysis focuses on the production, circulation, and consumption of scarce forms of knowledge. To explore situated knowledge of border security practices, I develop an approach to multi-sited event ethnography to observe and interpret knowledge that may be hard to access at the security fairs. The analysis focuses on mechanisms for disseminating and distributing scarce forms of knowledge, technological materializations of situated knowledge, expressions of transversal knowledge of security problems, how masculinities structure knowledge in gendered ways, and how unease is expressed through imagined futures in order to anticipate emergent solutions to proposed security problems. The article concludes by reflecting on the contradictions at play at fairs and how to address such contradictions through alternative knowledges and practices.