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.
Look on the lower left of a check and you'll see a long string of numerals. The first nine digits are the routing number. The next symbol marks the end of the routing number and is followed by another batch of digits. This second string of numerals is the checking account number.