Terry uses his portable thumb unit to collect donations for the Hill Valley Preservation Society.


Fred, the driver of Cab B25 in 2015, uses his portable thumb unit to figure Biff Tannen's fare, while his parrot Priscilla looks on.

" "Hey, kid," the old guy called as Marty walked past, "can you thumb a hundred bucks to help save the clock tower?" He held out a silver box with the inscription "Portable Thumb Unit". / Marty hesitated. / "It's an important piece of history," the other guy added earnestly. The circular name patch over his pocket said his name was "Terry". "
—From Back to the Future Part II by Craig Shaw Gardner (quote, page 49)

A portable thumb unit was a rectangular-shaped handheld electronic wireless device with fingerprint scanning technology, used in 2015 to collect donations and other funds where a person was unable to access a teller.


One such charity collector was Terry, representing the Hill Valley Preservation Society, who came up to Marty McFly asking for a $100 donation to save the Hill Valley Courthouse.[1]

Portable thumb units were also used by taxicab drivers, such as Fred, the driver of Cab B25 from the Luxor Cab Company.[1]


  • In 2015, as well as prior years, rectangular-shaped handheld electronic tablets with fingerprint scanners are commonplace, and are used to make payments using fingerprints.