"During the presidential campaign, Trump lashed out at primary opponent Jeb Bush for suggesting that Trump would build a fence instead of a wall.
Jeb Bush just talked about my border proposal to build a “fence.” It's not a fence, Jeb, it's a WALL, and there's a BIG difference!
— Donald J. Trump (@realDonaldTrump) August 25, 2015"
The area in question was right on what looked like the end of some city street - no reason to not have a structure that allows visibility - especially around a populated area.