"Surfing is definitely one of the funnest board sports that I've ever done," Rostvold said. "There's kind of limitless expression in the fact that there are so many different types of boards out there and every surfer has their own unique and individual style."

A few years ago, Rostvold went with the club to surf in California in the late winter and experience the Pacific Ocean waves that are almost mythical on the North Shore. Another trip to the Golden State was on the horizon a year later and he needed, or maybe wanted, a new board. He had learned about process of shaping surfboards on his first trip to the West Coast and he decided to give it a try at the Castle Danger house where he now lived.

"I got to tour some shops and see their shaping bays and their glassing facilities and kind of got the run through of what goes into a board," Rostvold said. "The following winter, I was going out to California and I wanted a new board for that winter, a shorter one, so that's when the idea of how a board was made."

Shaping a surfboard is a very specialized task and requires very specific tools and resources. He built a shaping rack and acquired the tools he needed piecemeal, which prolonged the process longer than he wanted. He bought a planer and surform — or surface forming tool — and a polyurethane foam blank from California.

"I built each piece as I needed it and acquired each tool as I needed it, which is a kind of a slow way to build a surfboard," he said.

He drew the lines onto the surface of the board to shape the rails where the surfer rides. The board slowly emerged from the blank as Rostvold wore a respirator mask to ensure he doesn't inhale the foam dust.

After finishing his own board, which included covering the board in fiberglass cloth and a hardening resin, Rostvold was quickly commissioned to do two more. He realized he could make money building surfboards, and Castle Glass Surfboards was born.

He transformed a bedroom of his house into a shaping room so he could work on boards throughout the winter. He created lighting to illuminate the rails on the boards.

He enjoys the creative process of bringing a board from a mental concept to actualization.

"The most fun part is seeing your work come to life in the finished product," he said. "It's something that is only an image in your mind and your putting hand tools and power tools on a piece of foam and seeing it come about."

Currently, Rostvold is only shaping custom boards by order. So far, he's built and sold 30 boards that range in cost from $500 to $1,000. He is also raising capital to start building production boards. There aren't any surf shops in Duluth or on the North Shore, but he is working with shops in Wisconsin and Michigan that may stock his boards. He's also building support by creating Castle Glass merchandise like stickers and T-shirts.

"There's a lot of enthusiasm behind shaping and board building, but not everyone wants to surf," he said. "A lot of folks want to get behind what I'm doing and support something local, so that's the way they can support it — on just a $20-or-so purchase."