For Kevin Martyn, who fixes wheelchairs for high-impact rugby matches at the Tokyo Paralympics, working with sports gear and prosthetics is the "ultimate puzzle".
The 37-year-old Canadian is one of the dozens of specialist technicians who have come to Japan to make sure athletes aren't let down by their equipment.
"I love these chairs, because they're built to hit each other as hard as they can," Martyn told AFP as he adjusted the height of a wheelchair's front bar in a pop-up workshop at Yoyogi National Stadium.
"They are built for impact, they get broken, and I love being able to be here to help fix them, so they can keep playing hard in a really intense sport."
He works for Ottobock, a German firm that has run repair shops at every Paralympic Games since 1988, with more than 100 staff from 23 countries on hand in Tokyo.
They are at venues and the main workshop in the Paralympic Village, where runners come to get their blades serviced and archers can have a custom fingerguard 3D printed.
"Every single job is different, and a challenge, and sometimes you don't know what you're going to get. For me, it's the ultimate puzzle to solve," Martyn said.
Ottobock brought 17,300 spare parts to Tokyo so it can carry out repairs quickly and efficiently.
But the company believes the load could one day be reduced through 3D printing, which is on trial in their workshop for the first time at the Tokyo Games.
"We shipped four large containers from Europe to here, because we never know what the issue is -- we need to bring a lot of stuff," said Peter Franzel, Ottobock's head of global events.
"We have a lot of tyres, screws, nuts and bolts... we have the knee joints for prosthesis, we have the feet, we have the sockets, we have the liners."
For now, 3D printing is too slow to make large items in time for competitions, and the products could be sturdier.
But Franzel has high hopes for the technology: "Maybe in the future, we only ship one 3D printer, and we print out everything we need."
The team had already completed 800 repair jobs in the 10 days to Friday, and are on call 24 hours a day for emergencies.
But Martyn said he has enjoyed it all.
"Being able to help even a little bit -- changing a tube, or fixing a crack -- you know you're making a big difference."