[ikonst]

Make you perform a challenge that's possible with two hands but impossible with one.

See https://www.youtube.com/watch?v=9aMXEOAvfb4

[crooked-v]

What happens when people try to do this while driving with their knees?

[ubersync]

Or, people who don't have two hands?

[sankae]

Man without arms denied loan because he can't provide finger prints

http://www.bbc.co.uk/newsbeat/article/38077013/man-without-a...