He climbed one of the world's most difficult boulders after practising on a 3D model

5:47He wanted to climb one of the world's most difficult boulders. So he practised on a 3D model

When Will Bosi finallyreached the top of the Burden of Dreams, he could barely believe it.

On April 12, the Scottish climber becamethe second person ever on record to successfully ascend the notoriously difficult to climb boulder in Lappnor, Finland.

"Up until even a month before going, I wasn't sure it would be possible for me maybe ever," Bosi told As It Happens guest host Helen Mann.

"So,like, ending up on top of the boulder was just completely surreal. I just couldn't stop smiling, to be honest, for hours."

And all it took were several sleepless nights, countless frustrated falls, scraped and bloodied fingers, and perhaps most importantly a 3D-printed replica of the rock itself.

Short, but difficult

At about four metres, the Burden of Dreams is not particularly tall. But that doesn't mean it's easy.

Bosi practises a type of climbing known as bouldering, wherein climbers scale small rock formations or artificial rock walls without the help of ropes or harnesses.

The goal is to solve what are known as "boulder problems." Essentially, that means climbing small, but tricky, routes that requirea specific, and often physically challenging, sequence of moves.

The Burden of Dreams is considered one of the if not the most challenging boulder problems on the planet. Ithas the highest possible difficulty rating across several different scales.

Finnish rock climber Nalle Hukkataival is the only person known to have successfully climbed it before Bosi. And,according to Outside Magazine,it took him 4,000 tries.

So what makes it so hard? First of all, it's extremely steep about 45 degrees the whole way up and mostly smooth.

The few holds that a climber can grab onto are "absolutely desperate," Bosi says, meaning they're tiny, spread far apart and jagged to the touch.

"Think of trying to hold onto almost a little bigger than a credit card [or] razor blade edges on a really steep overhanging wall, and then doing five big, difficult moves between them where you're having to really, like, throw your body," Bosi said.

"Because theholds are sharp, it cuts into your skin really fast. So you can actually only give a couple goes before it will cut through and you'll start bleeding and you'll have to stop."

Bosi didn't count how many times he tried and failed to scale the boulder before he was finally victorious.But he spent about two weeks in Finland trying it over and over again, repeatedly falling in frustration onto the mats below.

"Each move is so hard, that to do it, you need to have your hands in exactly the right place," Bosi said."If you were to do the first move and hit the hold even just two millimetres with your fingers slightly to the wrong side, then you might be able to hold that move, but then you won't be able to do the next one."

In between practice sessions, he says he could barely focus or sleep.

"You're just thinking about this all the time," he said.

3D-printed replica

But Bosihad some advantages his predecessor did not. Before he tried it in person, hetrained on a 3D model at the Lattice Training gym in Sheffield, England, where the Edinburgh-born climber currentlylives.

A fellow climber, Aidan Roberts, took 3D scans of the boulder's holds after several failed attempts at climbing it himself, Bosi said, then had replicas of those holds printed in plastic.

Then, the folks at Lattice Training attached those printed holds to a climbing wall, tilted at 45-degree angle, and spread them out at the same heights and distances as they are on the actual rock.

"It's almost an exact replica of the real boulder," Bosi said. "So I was able to have a lot of sessions on that, and really train for it before going out, which made a huge difference."

WATCH | Practisingthe Burden of Dreams at the climbing gym:

If that sounds a bit like cheating, Bosi is quick to point out that climbers have been building replicas for decades. It's only the 3D printing part that's new, allowing the practice climbs to be that much more precise.

"There were comments of people wondering if it's getting too close to the real thing and you're taking the sort of experience and the mystery out of it a bit," Bosi said.

"But I think because it is still not a perfect replica it's still plastic, it's hard to get the wall exactly the same angle that I don't think that many people were too worried about it."

A short film about Bosi's climb, produced by Crimp Films and Band of Birds, titledBurden of Dreams, will premiere Tuesday at the Climbing Hangar in Sheffield.

Bosi, meanwhile, already has his eye on the next prize. First, he says he plans to tackle some other highest-rated boulderproblems in the world.

And if that works out, he says he'd like to scout the wilderness for a new boulder problem to solve and become the first to ascend it.