In the broad, Platonic sense, President Trump’s pledged border wall is what it always was: A wall, on the border with Mexico, for which Mexico will pay. In a specific sense, despite Trump’s assertions to the contrary on Thursday morning, the composition of that wall has changed several times since he first proposed the idea, months before he ran for office.

Trump’s insistence that the wall is the same now as it always was follows The Washington Post’s report that White House Chief of Staff John F. Kelly described Trump’s description of the wall during the campaign was “uninformed.”

“A concrete wall from sea to shining sea” won’t be constructed, Kelly, reportedly told a group of lawmakers. In some places, there would be a concrete wall, though that “would be good in only certain places.” In other places, the terrain would obviate the need for a wall; in some places, aircraft and land patrols would suffice.

This argument clearly made Trump mad. During his morning executive time, he tweeted a rebuttal.

That’s not exactly true. I went back over what Trump said about the wall during the campaign, finding that his proposals have changed in significant ways. And to illustrate, I’ve commandeered my 1-year-old son’s Duplo blocks.

April 2015

Months before he actually declared his candidacy, Trump spoke at a town hall in New Hampshire and answered a question about immigration with a description of his wall — for which Mexico cover the costs.

“I will build the best wall, the biggest, the strongest, not penetrable, they won’t be crawling over it, like giving it a little jump and they’re over the wall, it costs us trillions,” he said. “And I’ll have Mexico pay for the wall. Because Mexico is screwing us so badly. I will take it from out of just a small fraction of the money they’ve been screwing us for over the last number of years.”

He didn’t specify a height for the wall at that point. Let’s start, though, with a wall that’s 30 feet high. For scale, I’ve included Duplo Man (who may have an actual name, I don’t know), who for our purposes will be assumed to be 6 feet tall. (That’s three inches shorter than Trump himself, according to his recently released physical.)

August 2015

Now a candidate, Trump offers some more specifics at a campaign event.

“I already know what it should look like. … I’m a great builder. What do I best in life, I build. Your infrastructure is crumbling. Isn’t it nice to have a builder? A real builder. So you take precast plank. It comes 30 feet long, 40 feet long, 50 feet long. You see the highways where they can span 50, 60 feet, even longer than that, right? And do you a beautiful nice precast plank with beautiful everything. … You put that plank up and you dig your footings. And you put that plank up — there’s no ladder going over that. If they ever go up there, they’re in trouble, because here’s no way to get down. Maybe a rope.”

He wanted the wall to be beautiful, he said, “because maybe someday they’ll call it the Trump Wall. Maybe. So I have to make sure it’s beautiful, right?”

That’s pretty clear: A concrete slab wall. An engineer mapped out what this would entail, finding that it would contain three times as much concrete as the Hoover Dam.

Later in August

Later that month, Trump first broached the idea that you wouldn’t need to cover the whole length of the border.

October 2015

He addressed that issue in more detail during the third Republican primary debate.

“They built the Great Wall of China. That’s 13,000 miles. Here, we actually need 1,000 because we have natural barriers,” he said. “So we need 1,000.”

This jibes with what Kelly told the lawmakers. In some places, mountains or rivers — or, in the case of our Duplo blocks, stacks of flowers — would by themselves prevent passage, so no wall would be necessary.

Trump went on.

“We can do it for $10 billion to $12 billion, and it’s a real wall,” he said. “This is a wall that’s a heck of a lot higher than the ceiling you’re looking at.”

Over the course of 2016, we tracked the ever-evolving height of Trump’s wall. That included this comment, offered in the Moores Opera Center on the campus of the University of Houston. We called the university to find out how high the ceiling of the facility was, learning that it was 45 feet high.

A “heck of a lot higher” than that we pegged at 55 feet. Here’s how tall that would be, using up all of my son’s two-by-two Duplos.

But that height, too, was short-lived.

February 2016

Trump ups the ante during a campaign rally.

“I get a call from one of the reporters yesterday, and they said, ‘The President of Mexico said they will not under any circumstances pay for the wall,’ ” he told the crowd. “They said to me, ‘What is your comment?’ I said, ‘The wall just got 10 feet higher.’”

I don’t have the Duplo blocks to show how high that would be.

June 2017

Trump starts digging into the details, proposing to a crowd in Iowa a wall that would not need Mexico’s money because it might pay for itself.

“I’m thinking of something that’s unique, we’re talking about the southern border — lots of sun, lots of heat. We’re thinking about building the wall as a solar wall, so it creates energy and pays for itself. You’re the first group I’ve told that to: a solar wall. Makes sense, let’s see. We’re working it out, let’s see. A solar wall. Panels, beautiful. Pretty good imagination, right? My idea.”

This idea soon gets scrapped. Which is a good thing if only because the depiction of solar panels in plastic blocks is tricky. This is the best I could come up with.

July 2017

Trump suddenly introduces a new component: The wall must be see-through so that people aren’t crushed by flying bags of drugs.

“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.”

I talked to experts who offered an important reassurance. People can’t throw 60-pound bags over 50-foot walls. If they used medieval siege weaponry, though, the picture changes.

Anyway. Our wall now looks like this.

That, then, is the current manifestation of the wall. But why did Trump suddenly advocate the addition of windows?

January 2018

He explained in an interview with the Wall Street Journal earlier this month.

“The other thing about the wall is we’ve spent a great deal of time with the Border Patrol and with the ICE agents and they know this stuff better than anybody, they’re unbelievable. … I had meetings with them, they need see-through. So, we need a form of fence or window. I said, why you need that — makes so much sense? They said, because we have to see who’s on the other side.”

There you go. He also argued that adding windows was cheaper than adding cameras.

“Now on the wall we have cameras and we have highly sophisticated equipment, but the wall — the Border Patrol tells me the other way’s more expensive,” he told the Journal. “It’s not less expensive. We have to have vision through the wall. This is going to be state-of-the-art wall; this will be state of the art. But, I can fully understand why you’d have to have vision. I’d like to be able to see three or four hundred yards instead of: We’re at a wall — we have no idea who’s on the other side.”

How additional agents positioned to look through those windows is cheaper than adding video monitoring systems isn’t clear, though one can see how the Border Patrol might endorse that argument.

There is one aspect of the wall on which Trump hasn’t budged, even as those around him — including Kelly in that meeting with lawmakers — have acknowledged the impossibility of the proposal.

Mexico, Trump continues to insist, will pay for the wall. Another tweet from Thursday morning.

If you are curious, Duplo blocks are not manufactured in Mexico. They are made in Hungary.