As the novelty of makerspaces in libraries slowly fades, this study examines how participation, expertise, and embeddedness in the library organization and surrounding community are sustained in library makerspaces. Based on interviews with makerspace practitioners in 13 Danish libraries, practices of maintaining, scaling, replicating, and evolving library makerspaces are analyzed. The findings propose a variety of practices and tensions concerning sharing ownership with user communities; scaling and prolonging users’ participation; building expertise through documentation, repetition, and sharing; collaborating with local community partners; and embedding makerspace practices into existing library practices, resources, and values. The results inform a discussion of participation, expertise, and embeddedness, which are distilled into three guiding principles that can help libraries reflect and address the sustainability of their makerspace over time.