SAN DIEGO — The scene played out like a segment on the QVC shopping channel. In making this one-of-its-kind product, the host proclaimed, no expense was spared. It was crafted from the finest steel and the heaviest concrete. This was “the Rolls-Royce version” — so strong, so imposing that no human could scale it, not even a champion mountain climber. Twenty had tried and failed, he said.

The pitchman was President Trump. And the product was his much-ballyhooed border wall.

Trump used just about every sales trick he honed as a real estate developer and promoter here Wednesday to showcase a newly built section of barrier along the U.S.-Mexico border.

Immigrant rights advocates and other critics denounce it as a menacing testament to inhumanity and cruelty, but Trump hawked the massive fence as a feat of innovation and ingenuity — the physical manifestation, although for now only in partial form, of his signature campaign promise.

Taking reporters on an afternoon pilgrimage to a dusty construction site in the Otay Mesa area of San Diego, Trump boasted of the structure’s design features as if he were still in his pre-presidential life pitching investors on a glimmering new condo building.

“We have a wall the likes of which very few places have ever seen,” Trump said at the start of a 37-minute presentation that he and his top immigration officials made to journalists. “What they’ve done is beyond.”

The president was armed with facts and figures. He talked up the wall’s height (between 18 feet and 30 feet, depending on the risk assessment of the location); its projected length (“close to 500 miles” by the end of next year); and its depth (the steel bollards and concrete go about six feet into the ground).

“It really is virtually impenetrable,” Trump said, comparing it favorably to previous barriers. “Any walls that were put up, we can knock down very quickly, very easily. This wall is not something that can be really knocked down.”

Trump tried to brush over the reality that Mexico is not paying for the barrier, as he had promised throughout his 2016 campaign. Construction is being funded with U.S. taxpayer money after the president used emergency powers to tap funding that Congress had allocated for Pentagon projects.

Trump said that he tried to lower the cost. “I said, ‘Fellas, how about doing a less expensive version?’ ” he told reporters. “They said, ‘Well, this is the version that works, including the poured concrete in the steel with the rebar and everything else.’ That’s the Rolls-Royce version.”

Trump played up the dangers from which the barrier is protecting Americans. “Tijuana is right over there,” he said, referring to the notoriously crime-ridden city on the Mexico side. Two barriers were being erected here: An 18-foot structure on the Mexico side and a 30-foot structure on the U.S. side, with a road between them on which U.S. agents could patrol.

Trump promoted the barrier’s design as all the better to keep unwanted migrants on the Mexico side. Steel bollards, which look like hard-edge industrial tubes, are rooted deep in the ground and rise straight up into the sky. Concrete is then poured into the hollow interior to fortify the structure.

“If you think you’re going to cut it with a blow torch, that doesn’t work because you hit concrete, and then if you think you’re gonna go through the concrete, that doesn’t work because we have very powerful rebar inside,” Trump said.

Trump explained that the steel panels atop the bollards are designed to absorb heat from the broiling sun, a mechanism to further scare away would-be intruders.

“You can fry an egg on that wall,” Trump said. “It’s very, very hot, so if they’re going to climb it, they’re going to have to bring hoses and water, and we don’t know where they’re going to hook it up because there’s not a lot of water out here.”

Although he had once advocated for the barrier to be painted black to better absorb heat and to have spikes at the top, features intended to injure perpetrators, Trump said the government was keeping the steel natural — “a good, strong, rust color” — while reserving the option to paint it at a later date.

Trump said design prototypes had been stress-tested. “We had 20 mountain climbers,” he said. “That’s all they do. They love to climb mountains. They can have it. Me, I don’t want to climb mountains, but they’re very good. Some of them are champions. And we gave them different prototypes of walls and this one was hardest to climb.”

“This wall can’t be climbed,” Trump added. Later, he allowed, “I guess maybe one of the greatest pole vaulters in history can get over the low one, but it’ll be very painful when they land.”

Trump was flanked by top immigration officials, who nodded in agreement with the president’s declarations and offered their own testimonials. They were like certified experts giving a new product the Good Housekeeping Seal.

“This design, it’s a game-changer,” said Mark Morgan, acting commissioner of Customs and Border Protection.

At one point, Trump nearly gave up operational secrets.

“One thing we haven’t mentioned is technology,” he said. “They’re wired so that we will know if somebody’s trying to break through, and you may want to discuss that a little, General.”

Lt. Gen. Todd Semonite, the commanding general of the U.S. Army Corps of Engineers, which oversees construction of the border barrier, demurred.

“Sir, there could be some merit in not discussing that,” he said.

So Trump opted instead for a casual summary: “I’ll just tell you they’re wired, okay?”

Trump later touted the barrier’s technological advances. “Now we have a world-class security system at the border,” he said. “I would think that there’s no place like this anywhere. No place has anything like this or even close to it. Other places have guards, and unfortunately they have machine guns and they have electrified fences — you touch them and you get electrocuted — but we don’t do that.”

As the event went on, it may have sounded to some like Trump was on an ego trip, but Morgan sought to dispel that notion.

“Sir, if you don’t mind, I think this is important to talk about,” Morgan said. “There’s a false narrative out there that this wall is the president’s ‘vanity wall.’ I’m here to tell you right now that’s false.”

Trump seemed delighted by the acting commissioner’s performance. As Morgan spoke, the president locked eyes with a Washington Post reporter, smiled widely and nodded, as if to signal that he knew exactly what Morgan was up to.

Trump was clearly taken by the steel fortress rising from the dirt and he hoped the journalists were, too. “I wanted to have you here because nobody would believe this unless they see it,” he said. “I hope you’re impressed. . . . This is top of the line.”

As he finished, the president was informed of a tradition at the border that anyone who works on the wall signs it. Trump, who autographs everything from photographs of himself to news articles about himself, leaped at the chance.

“Sign it?” he said. “I’ll sign it. Let’s go.”

Aboard Air Force One for the flight back to Washington, Trump strode back to the press cabin to boast more about his achievement. “I’m glad you got to see it,” he told reporters.

The president sounded like he was seeking affirmation from people bound by professional ethics not to provide any.

“I hope you like the wall, by the way,” he told the traveling press pool. “Do you like the wall?”

Trump fielded questions about other topics, but before returning to his cabin at the front of the plane, he came back to what had been at the top of his mind.

“I hope you see the wall is what it is,” he told the journalists. “It’s a great structure and it’ll really do the trick.”