"Borders are geographic boundaries of political entities or legal jurisdictions, such as governments, sovereign states, federated states, and other subnational entities. Borders are established through agreements ...
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between political or social entities that control those areas; the creation of these agreements is called boundary delimitation.
Some borders—such as a state´s internal administrative border, or inter-state borders within the Schengen Area—are often open and completely unguarded. Other borders are partially or fully controlled, and may be crossed legally only at designated border checkpoints and border zones may be controlled." - (en.wikipedia.org 29.02.2020)