Executives of The New York Times Company undertook security studies in planning its new headquarters after 9/11, focusing on terrorist threats but apparently never considering that the building — sheathed in rows of horizontal ceramic bars — could become an urban ladder for climbers, as it did twice on Thursday.

Michael Golden, the vice chairman of the Times Company, said he did not recall any discussion about the possibility that someone could try to scale the 52-story building. "I don't remember that, no," he said on Friday.

A day after one man followed by another used the building as a giant jungle gym, the executives responsible for security and engineering met with police officials. The Times Company and Forest City Ratner, the real estate company that owns 48 percent of the building, agreed to a short-term plan to keep would-be climbers away.

The plan, which involved hiring security guards and putting up plywood barriers to close gaps that climbers could squeeze through on their way up, reflected both the seriousness of the issue and the unexpected sense of vulnerability at the Times Building. The ceramic rods are one of the building's most distinctive features, a lattice of silvery-gray bars that forms an extra outer skin, several feet beyond the plate-glass windows that run to the ceiling on each floor. The plywood installed on Friday gave a construction-zone touch to a metal-and-glass building whose look had been carefully thought out.

The skyscraper, on Eighth Avenue between 40th and 41st Streets, is the work of the Italian architect Renzo Piano, who declined to be interviewed on Friday, saying that Mr. Golden had specifically instructed him not to speak to the newspaper's reporters. Mr. Golden acknowledged this, saying, "I've told Renzo, I don't think there's any good that comes from this kind of publicity."

The design work on the building began long before the 9/11 attacks, and after the destruction of the World Trade Center, Mr. Golden said, "there was a great deal of discussion and design changes made for the security" of the new Times Building — "not for people climbing outside, but the kinds of issues 9/11 raised." He would not discuss the details.

He said he was deeply troubled by Thursday's events. "I hate the fact that it happened — there's no good that comes of it," he said.

But as to whether the Times Company would consider removing the ceramic rods, he said, "No."

The first climber, a French stuntman named Alain Robert, said in an interview on Friday that the ease of climbing the Times Building was quite obvious to him — on a difficulty scale of 1 to 10, he rated it a 1. Even so, he said, his stunt required some planning. He said he had scouted the building some weeks ago and had even done a brief trial climb about 2 o'clock one morning, apparently undetected.

Ever since the mountain climber George H. Willig scaled the south tower of the World Trade Center in 1977, architects have been careful to avoid making tall buildings easy to climb. "There is a certain logic to how accessible you make the building — how readily are you actually creating a ladder up to the top?" said T. J. Gottesdiener, a managing partner at Skidmore, Owings & Merrill, which designed the Freedom Tower being built at ground zero.

"This is going to be a real big consideration on everybody's list" because of the two incidents at the Times Building, he said.

For the Freedom Tower, Mr. Gottesdiener said, the architects designed a base of vertical, prismatic glass to avoid climbable ledges. Security issues regarding the facade were discussed at length. "It's very practical — whether people can actually come and stick their toe in it and start to climb up it," Mr. Gottesdiener said. "You've got to think about what kind of opportunities you're presenting to people."

Soon after The Times moved into the building last year, security duties were divided. Security in the lobby was split between officers who worked for the Times Company and others who worked for First New York Partners, a management and operations arm of Forest City Ratner. Under that arrangement, the Times Company was responsible for security on its floors — 2 through 27, and part of 28 — and First New York was responsible for the remaining floors and the exterior of the building.

Abbe R. Serphos, the director of public relations for the Times Company, said that the arrangements had changed in recent weeks. She said that security employees of the Times Company had "started to report to" First New York Partners. "They oversee our security team now," Ms. Serphos said.

She said the Times Company's longtime director of security, Jay McKillop, had left recently and "moved on to another opportunity." Reached by cellphone on Friday, Mr. McKillop declined to discuss the security planning for the Times Building or say whether the issue of climbers had been considered.

John Garrity, an employee of First New York Partners who is director of security for The New York Times Building, also declined to comment. He said he had been instructed not to speak by executives of the Times Company.

No one could recollect a climbing incident at The Times's former headquarters on West 43rd Street.

Mr. Robert and the other climber, Renaldo Clarke of Brooklyn, were both charged with reckless endangerment, criminal trespass and disorderly conduct. Both were released on bail on Friday.

Steven Emerson, the executive director of the Investigative Project on Terrorism, a nonprofit public interest group in Washington, said the fact that two climbers scaled the building in one day with such ease showed flaws in preparedness. Neither man used any equipment, unlike Mr. Willig, who designed special climbing apparatus for his World Trade Center ascent.

Mr. Emerson said that any news media organization needed tight security, and added that he was surprised that the Times Building did not have "prohibitive perimeter security" — something at street level to stop would-be climbers from getting a foothold. "I just naturally assumed that in the construction of the new building they would have accounted for the fact that it would be a natural magnet, particularly in a post-9/11 world," he said.

Mr. Robert said in an interview on Friday that he chose the Times Building because climbing it seemed simple.

He said his prime goal was to ascend as quickly as possible to a height beyond the reach of the Fire Department's ladders, which he figured was about 200 feet.

Once he knew he could not be stopped, he paused to unfurl a banner and attach it to the building. The banner promoted thesolutionissimple.org, the Web site of an environmental group that sponsored his climb.

Mr. Robert, a slight man with shoulder-length brown hair and a nose bent like a prizefighter's, said he was neither flattered nor insulted by Mr. Clarke's same-day ascent.

"Since climbing this building is like climbing a ladder, it doesn't mean he is a good climber," Mr. Robert said. "For me, it doesn't change anything."

Mr. Robert said he had been planning to climb the Times Building for several weeks. He described it as a "perfect target" because of the ladderlike curtain of rods, which runs from the second floor to the roof. To reach the lowest rods, he shimmied up a beam from the sidewalk on 41st Street to a glass overhang, he said.

Al Baker and Patrick McGeehan contributed reporting.