SAN DIEGO, Cali.—On a slab of a desert wasteland that makes up the California and Tijuana, Mexico border, the future of border security stands some 30-feet tall.

In late September, six companies working with eight different designs started building giant models, or prototypes, of a new border wall.

A new “wall,” or fence, has long been a promise of President Donald Trump, who says it’ll drastically increase border security while decreasing illegal immigration.

The men and women on the ground in the San Diego sector of the U.S. Customs and Border Protection Agency echo that thinking.

"Whether it's illegal immigration, narcotics, whatever that threat may be,” said Roy Villareal, the San Diego sector acting chief. "We may have a singular design for somewhere on the border, or we may have a combination of designs."

Villareal said the government will start testing the designs for potential weakness in mid-to-late November.

Agents say they need to be impregnable on multiple fronts.

“What we're looking for is it not to be easily scalable, climbable, or for rudimentary tunnels to not be easily made," said Eduardo Olmos.

A CBP agent for a decade now, Olmos says four of the prototypes are more traditional “concrete” structures, while four others are intended to be slightly more abstract. Major construction finished late last week.

"For the ones that people might look at and say, ‘You can't see through them?’ Well, we might have cameras on top," said Olmos.

The San Diego sector of the border experienced a major drop in illegal immigration after expanding its wall in the 1990s, according to the CBP figures.

In 1995, there were more than 500,000 illegal apprehensions in the area. That figure dropped to roughly 32,000 by the 2016 fiscal year.

But people who legally make the journey on a regular basis, aren’t sure an expanded wall will really deter folks from coming illegally.

“If I don't have no papers, and I saw the wall, meh, If I want to cross, I'm going to cross one way or the other," says Emilio Buscamante, who lives in Tijuana.

He crosses into California five days a week for a job at IHOP. “I believe there is a different way to fix all the problems," he said.

In Texas, where there is some 1,200-plus miles of border, the idea of a massive wall covering every inch has been met with skepticism.

Michael Evangelista-Ysasaga runs Penna Construction, which actually bid to build one of the border prototypes.

He says there are some places in the Lone Star state, particularly on mountainous regions like Big Bend, where a fence just doesn’t make sense.

"Some of the rock faces fall at more than a 90 degree angle. I don't know how anyone is going to put a wall there except to blow up the rocks, excavate & create a level surface,” he said, adding that such a process would be too costly.

Ultimately, the Penna Group was passed over for the project. They’re considering legal options, partly because their boss thinks the entire bid process was filled with mistakes.

"Most of the companies actually lifted from our designs,” Ysasaga said.

One Texas firm did get approval to build.

Texas Sterling, based in Houston, erected one of the “non-concrete” prototypes at the work site. It features a jagged, spiked top to deter would-be climbers.

The government dished out some $300,000 to $500,000 for each contractor to build their model.

But money for any mass expansion is still very much up in the air, with Congress yet to approve anything resembling the $21 billion dollar funding estimate that would be necessary for a new wall project.

Villareal said even if there isn't a new major construction project, the new designs could help enhance the 600-plus miles of existing fence, especially when combined with surveillance and other patrol features.