One of the things with the wall is you need transparency. You have to be able to see through it. In other words, if you can’t see through that wall — so it could be a steel wall with openings, but you have to have openings because you have to see what’s on the other side of the wall.
And I’ll give you an example. As horrible as it sounds, when they throw the large sacks of drugs over, and if you have people on the other side of the wall, you don’t see them — they hit you on the head with 60 pounds of stuff? It’s over. As crazy as that sounds, you need transparency through that wall.
– Republican President Donald H. Trump, July 14, 2017