Terms used in international trade, such as delivered at frontier, outline who bears the risks and expenses of transporting goods under international transactions. A variety of terms exist for various methods of transportation. Delivered at frontier is most often used when using ground transport, such as truck or rail, to supply the goods.
It's important to realize that because this is a legal term, its exact definition is much more complicated and differs by country. It is suggested that you contact an international trade lawyer before using any trade term.