An injured supporter of Kenyan opposition leader Raila Odinga receives assistance in Nairobi, Kenya on November 17, 2017. Kenyan police have used tear gas and water cannons to disperse supporters of opposition leader Raila Odinga who are trying to gather near the country's main airport and Uhuru park to welcome him back from an overseas trip. (Photo by Baz Ratner/Reuters)

Performers participate in the Day of the Dead parade on Mexico City's main Reforma Avenue, Saturday, October 28, 2017. Mexico's capital is holding its Day of the Dead parade, an idea actually born out of the imagination of a scriptwriter for the James Bond movie “Spectre”. (Photo by Eduardo Verdugo/AP Photo)

Kika-evolution, 5, an Auguste clown, poses for a photo during Mexico’s 17th annual clown convention, La Feria de la Risa, in Mexico City, October 23, 2012. Approximately 500 clowns gathered at two local theaters in the capital city to exchange ideas, compete for laughs and show off their comedy performances. (Photo by Anita Baca/AP Photo)

A Polish Air Force MIG-29 fighter (R) and an Italian Air Force Eurofighter Typhoon fighter patrol over the Baltics during a NATO air policing mission from Zokniai air base near Siauliai, Lithuania February 10, 2015. (Photo by Ints Kalnins/Reuters)

Secondary school students perform a barefoot “pilgrimage of suffering” to support the Occupy Central civil disobedience movement at the Admiralty protest site in Hong Kong November 30, 2014. It has been two months since police first fired tear gas to disperse demonstrators from the main protest site in the Admiralty district next to government offices in the heart of the Asian financial centre. (Photo by Bobby Yip/Reuters)

Interpolitex - the largest national forum of homeland security is the only national security fair of federal status and importance. It is held to provide manufacturers, suppliers and users special equipment and weaponry with an efficient tool for implementing a wide range of advertising and marketing objectives, monitoring of the market and deal-making. (Russia, Moscow, October 2011)

Farmers clash with riot policemen during a protest outside the Greek Agriculture Ministry on March 8, 2017 in Athens, Greece. Two people were detained after the windows of two police vans were smashed as approximately 1,000 farmers, mainly from the island of Crete, took part in the protest. (Photo by Nikolas Georgiou/ZUMA Wire/Rex Features/Shutterstock)

The Mexico – United States barrier – also known in the United States as the border fence, rotted fence or border wall – is actually several separation barriers designed to prevent illegal movement across the Mexico – United States border.