picture shows a self-service device to pay
to park in an unattended parking lot.
You need to fold up dollar bills and stuff
them "upwards" into
the numbered slot corresponding to your parking space.
To fit, a dollar bill has to be folded over
three times. It isn't easy. Imagine someone
with arthritis trying to do this.
you design something you need to think about the great
differences in the capabilities of the people that
will need to use it.