Jayson McCarthy, 12, was born without fingers on his left hand. That didn't stop him from being able to do many tasks. But Jayson could not grasp more than one object at a time. So Jayson 's father, Paul, created a Prosthesis , using a 3D printer. Now Jayson has fingers that open and close. "It was a do-it-yourself, father-and-son adventure," says Paul. When Jayson was a baby, his doctor advised his parents not to give him a prosthetic hand until he was in his early teens. "The doctor said Jayson should first learn to get full use out of the hand he was born with," says Paul. As Jayson got older, his father looked into _ a prosthetic hand, which can cost as much as $30,000. Paul found a more affordable solution. One day, Paul discovered a video on the Internet about Robohand, a prosthesis created with a 3D printer. He downloaded the free instructions and called Robohand's creators for advice. They told him all he needed was a 3D printer--which costs around $2,000--and some materials. Luckily, Jayson 's school had recently purchased a 3D printer and it offered to help Paul build the hand for Jayson n. "We used a soccer shinguard , cardboard , and tape. They cost about $10," says paul. With his new hand, Jayson can do things better. "I can help my mom more, because now I can carry two grocery bags," he says. Jayson 's father has already built several hands for Jayson. Jayson helps design each one. He says there's one thing in particular that he wants to do with a future prosthesis. "The goal," he says, "is to be able to tie my shoelaces ." Why did Jayson 's doctor disapprove of  his using a prosthesis in his childhood?
The prosthetic technology was underdeveloped then. A prosthesis was very expensive at that time. To use the disabled hand was important. The original hand could do many tasks.