The volume addresses a topic that is important for planning and politics as well as spatial social research, yet remains underexplored - the topic of borders. The volume is situated on different levels of discourse: on one hand, it engages with the theoretical and conceptual level concerning the issues of border drawing and crossing. On the other hand, it explores the significance of borders for the planning and action practices of actors through concrete examples. The aim of the volume is to reflect on current and politically relevant questions regarding borders in both spatial and social contexts. In addition to contributing to the geographical theory of the phenomenon of borders, it also aims to discuss their role as an everyday framework for action, as barriers, or as permeable contexts. The content includes theoretical and conceptual approaches.