Originally, the customs border between the Kingdom of Denmark and the Duchy of Schleswig followed Kongeåen. However, as of 21 April 1865, it was moved southwards to run between Plougstrup and the Wadden Sea.
All along the coast, smugglers tried to get away from the Customs inspectors. The Krydstold Authority existed from 1824 to 1904 and was governed by the General Chamber of Customs and Excise in Copenhagen. Krydstold Authority had 30 ships of varying sizes. Krydstold Authority was closed down in 1904.
In the Wadden Sea area there were customs stations in Nordby and Sønderho. Customs inspectors existed long before the Krydstold Authority was established, and it was not until 1851 that the Wadden Sea area became an official part of the Krydstold Authority. Nordby was the home port of ”Fanø”, a ship that covered the waters around Grådyb near Esbjerg, and was governed by the customs office in Hjerting. While the ”Wilhelm Carl” belonged to the customs house in Ribe, it was moored in Sønderho and covered the Knudedyb area around Mandø.
In addition, there were toldror stations at Vester Vedsted and Hejlsminde that kept an eye on wreckage and the coast from the landward side. Vester Vedsted Toldror station was closed down in 1903. It was replaced by a newly appointed customs officer on Mandø, and the border gendarmes took over the tasks of the toldror officers.