LOS ALAMITOS, Calif. — Seven-year-old Faith Lennox never thought much about putting a prosthetic limb where her missing left hand had once been.

Not until the little girl learned she could design her own, strap it on easily and then jump on her bike and pedal away at speeds previously only imagined.

With family members occasionally shouting “Be careful” and “Watch out for that car,” Faith firmly placed her new hand’s bright blue and pink fingers on her bike’s left handlebar and took off for a seemingly endless sojourn around the Build It Workspace on Tuesday morning. Inside, just a short time before, that hand had rolled off a 3-D printer that built it overnight.