Several candidates for the presidency in 2016 have proposed building more border wall along the nearly 2,000 mile frontier with Mexico to keep people from crossing into the U.S. illegally.
Here is what they have to say about a border wall.
Trump has been the most outspoken about building a wall, and insists he'll make Mexico pay for it.
"We're going to do a wall. We're going to create a border," he said during the third Republican debate in October. Trump also made reference to the Great Wall of China, and claimed that "Mexico is going to pay for the wall."
On his website, Trump reiterates his assertion that "there must be a wall across our southern border." In November, after eight Syrian Christians sought asylum and turned themselves in to officials in Laredo, Texas, Trump tweeted, "WE NEED A BIG & BEAUTIFUL WALL".
The Texas senator pledges on his website to "build a wall that works," and to "complete the wall," though he offers no specifics as to how he would do so.
The Florida senator says the most vulnerable sectors of the southwest border must be secured, according to his website. During the Republican debate in September, in response to a question, he said that "we must secure our border, the physical border, with a wall, absolutely."
In contrast to his rivals, Bush has said he considers a massive border fence to be unnecessary. "We don't need to build a wall," he told a group of Latino business owners in September.
A month before in McAllen, Texas, across the river from Reynosa, Mexico, the former governor of Florida told supporters that Trump's wall strategy "not based in reality."
At a November town hall campaign event in New Hampshire, where she was asked about securing the U.S.-Mexico border, the former New York senator and secretary of state stressed that she'd voted for the 2006 legislation that authorized the building of some 650 miles of wall.
"I voted numerous times when I was a senator to spend money to build a barrier to try to prevent illegal immigrants from coming in," Clinton said, "and I do think that you have to control your borders." She later apologized for using the term "illegal immigrants." She has not said whether she would extend the wall.
The independent senator from Vermont sees the importance of securing the border, but is opposed to building a fence to do so, according to his website.
"I also opposed tying immigration reform to the building of a border fence," he said during a speech in June to the National Association of Latino Elected and Appointed Officials.