WHS that are located on national borders (but are not transboundary). "Nation" here refers to one of the 203 sovereign states as named in List of Sovereign States.
World Heritage Sites connected to 'On National Border':
Saloum Delta With Gambia: a. . The Wiki entry for Gambia's Niumi NP states "The park is contiguous with Senegal’s Delta du Saloum National Park and Biosphere Reserve." b. The AB eval for Saloum states "it also includes the coastal marine area from the mouth of the Saloum River in the northwest,to the Gambian border in the south."