Do Border Fences Keep Migrants Out?

Evidence from the refugee crises shows that countries that have built fences have managed to successfully divert the flow of refugees to other routes;

Greece built a razor-wire fence in 2012 to block a short stretch of its border with Turkey that was a popular land crossing for migrants. It also increased security along the Evros River, which forms the remainder of the border. This is the first of several barriers that merely diverted the flow of migrants from Turkey, pushing them to Bulgaria or onto boats headed for Greek islands in the Aegean Sea.