It is one of the most enduring images from the silent film era, and arguably the movie stunt that led to the cliffhanging, skyscraper-loving action hero of today: the actor Harold Lloyd dangling from the hands of a clock on the side of an office building.

The film, “Safety Last!,” released in April 1923, was in many ways Lloyd’s zenith as a major Hollywood star. He is said to have come up with the idea of dangling from the side of a building after seeing a man scale one in Los Angeles.

But Lloyd wanted the stunt to be even more outrageous on film. Enter the clock.

“Harold was such a realist, and every scenario in his movies had to be a real event or a real situation for a person to be in,” his granddaughter, Suzanne Lloyd, 71, said during a recent video interview from her Los Angeles home. “The clock was another tool on the side of the building to perpetuate the stunt. He thought, ‘I can really play off of that.’”

And play he did. Lloyd’s character, The Boy, thinks up the idea of scaling a department store to win $1,000 offered by its manager to increase business — and hopes the stunt also will help him win The Girl. He begins his ascent, battling a flock of pigeons, a swinging window and a friend named Limpy inside the building who becomes as much of a danger as a helper.

As The Boy pauses on a window ledge, a buffoonish moment with Limpy causes him to fall back, saved only by grabbing the clock’s hands, which were conveniently positioned at 2:45 (when the longer minute hand is parallel to the ground).

For filming, according to Ms. Lloyd, a safety net was constructed on a roof about one floor below the action, though the scene was shot to look as though there was a sheer drop to the bustling streets far below. (Reports at the time said many in the audience covered their eyes or even fainted, and ambulances were parked outside some movie theaters.)

The Boy holds on, even as the clock dial tilts down and he is left hanging from the minute hand. There are a few failed attempts and a lot of slapstick, but, with the help of a rope, he finally makes it to the roof where The Girl is waiting with a kiss.

“The 1920s was an era of stunts, from planes to climbing buildings,” said Steven K. Hill, a curator at the UCLA Film & Television Archive in Los Angeles, which has been instrumental in saving and restoring hundreds of silent films, including a collaboration with the Criterion Collection on “Safety Last!” in 2012.

“Part of its appeal is that he’s not dressed like a construction worker,” Mr. Hill said. “He wears a straw hat and glasses and is well dressed. It can be seen as an image of his need for upward mobility.”

The Boy certainly is in pursuit of money — but for love. “The subplot in all of his movies was always about getting the girl,” Ms. Lloyd said. “Harold was really a romantic lead.”

Not only did The Boy get The Girl in “Safety Last!,” but Lloyd and the actress, Mildred Davis, were married shortly before the film was released. They stayed married until her death in 1969; Lloyd died in 1971. The couple had three children (Ms. Lloyd’s mother was Gloria, the eldest).

What makes the clock stunt even more impressive, Ms. Lloyd said, is that her grandfather was hanging on with only eight fingers. In 1919 he had lost part of his right index finger, his entire right thumb and part of his palm when he attempted to light a cigarette from the fuse of what he thought was a prop bomb for a publicity photo. But the bomb exploded, temporarily blinding him and putting him in the hospital for about two weeks. For years he wore a prosthetic glove to mask the injury in movies, but not in his personal life.

“I remember as a girl that he always wore a Rolex watch, but because he only had three fingers on his right hand, he would have to get someone to buckle the watch on his left hand,” Ms. Lloyd recalled. “Years later, he had a custom-made Rolex that was made of white gold and had a white face with silver numerals. And it didn’t have a clasp. It had a flexible watch band so that he didn’t have to ask anyone to help him.”

Lloyd’s fondness for clocks was evident to Ms. Lloyd as she grew up at Greenacres, her grandparents’ famous 44-room mansion in Beverly Hills, Calif. It was added to the National Register of Historic Places in 1982 and is now owned by the billionaire financier Ron Burkle (who also purchased Neverland, Michael Jackson’s California estate, in 2020).

“We had a lot of clocks in our house, including a jade clock in his den,” she said. “I remember once going watch shopping with him in Montreux, Switzerland, around 1961. He bought me a little blue watch with filigree that I wore on a chain around my neck. He later bought me a Cartier Tank watch when I was 18.”

Lloyd’s love of clocks might have been about making sure everything — and everyone — ran on time.

“Harold was always punctual, and my mom was constantly late,” Ms. Lloyd said with a laugh. “He bought several watches for her and adjusted the hands, and sometimes changed the time on the clock in her bedroom.”

“Harold would always say, ‘Move that clock up in Glo’s room to get her here on time,’” she said. “It worked!”