Department of Homeland Security testing of a prototype of the steel-slat design that Donald Trump favors for his Mexico border wall proved that it could be cut through with a saw, NBC News reports. A photo obtained by the network shows the slats with a gaping hole in the middle after experts from the Marine Corps were instructed to attempt to destroy the barriers with common tools. Testing by DHS in late 2017 showed all eight prototypes, including Trump’s favored steel slats, were vulnerable to breaching, according to a Customs and Border Protection report from last February. CBP spokesman Ralph DeSio said the prototypes “were not and cannot be designed to be indestructible,” and can only “impede or deny efforts to scale, breach, or dig under such a barrier, giving agents time to respond.” During the presidential campaign, Trump promised to build an “impenetrable, physical, tall, powerful, beautiful” wall on the border that would be paid for by Mexico.