touchback - (American football) a play in which the opposing team has kicked the football into your end zone.
From Wikipedia, the free encyclopedia. A check digit is a form of redundancy check used for error detection on identification numbers, such as bank account numbers, which are used in an application where they will at least sometimes be input manually. It is analogous to a binary parity bit used to check for errors in computer-generated data.
the ninth digit is the check digit it is calculated using an algorithm the check digit is used to validate the 8 digit bank routing number you can verify the authenticity of a check digit by running the algorithm yourself and comparing the check digit you calculate with the one that is printed on the check