SAN FRANCISCO (AP) ― Two men are roughly halfway through what has been called the hardest rock climb in the world: a free climb of an 900-meter section of exposed granite in California’s Yosemite National Park.

Tom Evans, a climber and photographer, has been chronicling Kevin Jorgeson, 30, of Santa Rosa, California, and Tommy Caldwell, 36, of Estes Park, Colorado, as they scale the wall using only their hands and feet.

El Capitan, the largest monolith of granite in the world, rises more than 900 meters above the Yosemite Valley floor. The first climber reached its summit in 1958, and there are roughly 100 routes up to the top. Of those, the hardest and steepest is called the Dawn Wall, which faces east toward the rising sun.

Many have climbed Dawn Wall, which has been described “as smooth as alabaster, as steep as the bedroom wall,” but the pair would be the first to free climb it using ropes only as a safeguard against falls.

The men eat, stretch and sleep in hanging tents suspended to the Dawn Wall. They don’t have the creature comforts of home, but they have kept in touch with the outside world thanks to social media ― tweeting, posting on Facebook, feeding information for blogs and keeping in touch with a bevy of supporters on the ground.

“The guys are doing great,” said Josh Lowell with Big Up Productions, which has been chronicling their climbs for the last six years. “(Monday) they are resting and trying to grow skin back on their fingertips so they can continue to do battle with the hardest climbing sections, which involve grabbing tiny, razor-sharp edges of rock.”

If all goes as planned, the duo could be at the top as soon as Friday or Saturday, Lowell said.

Evans said the two have a phone on their ascent, but they weren’t taking calls Monday because they were resting and “want no distractions while on the cliff.” The two also weren’t answering emails from roughly 450 meters above the ground.

There are 32 sections of the climb. On Sunday night, Lowell said Caldwell, climbing in the dark, completed the last of the three hardest sections of climbing, which was a major breakthrough.

In 1970, Warren Harding and Dean Caldwell (no relation to Tommy Caldwell) climbed Dawn Wall using ropes and countless rivets over 27 days.

The duo prepared for at least six years for the climb, according to friends and their personal websites. John Long, the first person to climb El Capitan in one day in 1975, said he speaks to the climbers several times a day.

“It’s almost inconceivable that anyone could do something that continuously difficult,” he said Monday, adding that he believes they spent the equivalent of a year’s time on the wall in preparation for the climb.