Jan. 29, 2008 -- Watch "World News with Charles Gibson" TONIGHT at 6:30 p.m. ET for the full report.
On mountains across the country, thrill seekers are flying off cliffs, traversing through trees and doing flips in the air. All with a piece of plastic strapped to their legs.
It's not your father's snow sled. It's called the Mad River Rocket and some users are taking this sled to the extremes.
"What they do is totally amazing. It might be the most proud I am of inventing this," said Dave Sellers, who has never done a flip on his Rocket.
Twenty-five years ago Sellers and some of his architect buddies wanted to have some control as they slid down the snowy hills of Northern Vermont. They also didn't like the idea of sledding face first, downhill, toward trees. Years of prototypes followed.
Early efforts required some rather whacky attempts to form a sled shell. "We took apart old electric ovens" to make a plastic forming machine says Jim Sanford, one of Sellers collaborators.
Finally, they came up with a couple solutions.
First, they decided to kneel on the sled and strap their legs down. To gain control, Sellers developed what he calls a "negative keel." Think of half a tube running down the bottom of the sled. That "keel" creates a monorail of snow.
"It makes this ribbon that is strong enough to hold you, and then you shift your weight and break the ribbon and go the other way . And bingo! We had it," said Sellers of his invention.
Rocket riders use their hands to turn the sled left and right. Sellers has dubbed this "free sledding."
In the last couple years the sled has been flying off store shelves. Seven thousand were shipped out this year by the Whitney Phillips, the president, chief assembler and shipping department of the Mad River Rocket Co.
The former competitive skier is a one-man Rocket representative and an extreme sledder in his own right. He faced the same sledding problems as the Rocket's inventor.
"I had no control as a kid and this one is just like skis or a snowboard. You can cruise right through the woods," said Phillips. And cruise he does with friends — darting between trees, even jumping off rocks.
Sellers and his friends are free thinkers. Part of the goal was to make something eco-friendly. They didn't like the idea of cutting down trees for ski runs. So, the Rocket allowed them to sled just about anywhere. The sled base is made of recycled plastic — the trimmings from the plastic garbage lids are made by an Ohio company.
"If you want to go gravity down anywhere in the country where there's snow, this is about as green as you can get," said Sellers. "The only trace is your footprint in the snow."
Free Sledding doesn't cost you anything except the price of the sled and some calories. One still needs to get to the top of the hill. As the young president of Mad River Rocket Co. likes to say, "You've got to burn to turn."
Sellers, an accomplished architect, says people talk to him more about his sled than his buildings. He doesn't seem troubled by that fact.
"If I can get people outside and enjoying the wilderness and having fun with it and being healthy, hey, that's great."