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President Trump has concerns about some of the proposed border walls because, as he put it, "They are incredible climbers."

POTUS -- aka walking soundbite machine -- was touring the US-Mexican border just south of San Diego, checking out potential designs for the wall when he warned engineers, "Getting over the top is easy. These are like professional mountain climbers."

Trump also suggested a see-through wall might be the best option, so Border Patrol agents can see what's cooking on the other side. Still, his biggest concern was for Mexico's word-class mountaineers. He added, "They can't climb some of these walls. Some of them, they can."