"The wall design shall be physically imposing in height", CBP officials said in contracting documents.
"Designs with heights of less than 18 feet are not acceptable", the document said.
In addition, the wall must resist attempts to penetrate through or under it.
The government outlines that the wall must be able to withstand a "sledgehammer, auto jack, pick axe, chisel, battery operated impact tools, battery operated cutting tools, Oxy/acetylene torch or other similar hand-held tools".
Both should be "aesthetically pleasing in color" and texture consistent with the general environment, but only from the north side.
One of the CBP contract requests calls for a solid concrete wall, while the other asks for proposals for a see-through structure.
In practice, the likely outcome is a few large government contractors overseeing a small army of subcontractors to build the wall. Soon afterward, the companies will build the prototypes in San Diego, where they will be tested.
Time-consuming legal challenges are sure to accompany Trump's orders detailing stricter enforcement at the border and in the interior of the country, said Leon Fresco, who led the Justice Department's Office of Immigration Litigation during the Obama administration.
The United States government on Friday released its stipulations for President Donald Trump's long-promised U.S. -Mexico border wall. It also includes a provision that contractors use American materials whenever possible.
Another construction giant, Elementia - partly owned by Mexican billionaire and Trump critic Carlos Slim - said it wants nothing to do with the project.
Although Trump's ascension to the White House has generally been a bad thing for Mexican companies, with the Mexican peso plummeting amid Trump's threats to renegotiate trade deals and tax Mexican imports, Cemex's stock has risen to eight-year highs in recent months.
As is standard with government contracts, a secretive selection committee will evaluate the proposals based on the merits of the design and the contractors' ability to complete the job.
Three of the most famous historical walls are now mainly in ruins: the Great Wall of China, Hadrian's Wall, and the Berlin Wall.
In a presentation to shareholders in NY on Thursday, company leaders said the "potential border wall" will drive demand for cement and therefore help the company's finances.