A steel-slat wall on the border, apparently, will only work if someone trying to cross doesn’t have a saw handy.

As the government shutdown marks its 19th day and President Trump continues to pressure Congress for $5.7 billion to construct his southern border wall — taking his case all the way to Texas in a trip to the border town McAllen on Thursday — security officials reportedly are aware their prototype can be easily sliced with a saw, according to NBC News.

In 2017, the Department of Homeland Security directed experts from the Marine Corps to try to destroy their Otay Mesa-based wall prototypes with some pretty common tools. Such steel designs have been utilized under previous administrations and are recently favored by Trump, who initially wanted a concrete barrier. Even if he were to pick another material or design to build his wall, though, the 2017 security tests found all eight prototypes under consideration were vulnerable to breaching. Photos obtained by NBC News show sizable chunks missing from the steel slats after someone took a saw to it. It’s not clear what sort of saw the person used.

Trump has cited a steel wall as a boost to the U.S. steel industry, which he’s long championed, even as he recently said it’s what the Democrats wanted, instead of concrete.

If the administration is successful in getting approval for the wall, it’ll still take billions of dollars, 10,000 construction workers and 10 years to get the proposed 1,000-mile structure up and running, according to the Washington Post. Trump promised during campaign rallies that his administration would construct an “impenetrable, physical, tall, powerful, beautiful” barrier to keep back Central American migrants seeking refuge in the United States. The president has floated the possibility of declaring a national emergency so he can access funding for the wall without getting congressional approval, if Democrats continue to deny him.