The activities of the States in the abovementioned field are very important. Theacknowledged state border is the main sign of the state’s sovereignty. The author considers the sequence and synchronization of the three States’ actions: the Russian Federation, the Republic of Lithuania and the Republic of Poland – in the demarcation of the junction point of state borders, clearly marked on the ground by the monumental border sign “Vishtynets”. The demarcation of this starting point of the Russian-Lithuanian state border allowed the Joint Russian-Lithuanian demarcation Commission to begin large-scale work on de-marking the Russian-Lithuanian state border, which ended with the signing the final documents on the demarcation of the Russian-Lithuanian state border in Vilnius during the 43rd final solemn meeting of the Joint Russian-Lithuanian demarcation Commission, which entered into force on 26 April 2018. As a result of the work done, 559 border signs were installed on the Russian-Lithuanian state border, and the border was first fixed by analytical points on the rivers, their coordinates are placed in “The catalog of coordinates and heights of border signs”.