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.
There are two sets of nine digit numbers printed across the bottom of every check. They are followed by a four digit number slightly set off from the others. The first two sets of numbers are your bank routing and checking account numbers; these remain the same from one check to the next. The last set of numbers is the check number and will be different depending on the actual paper check. Your bank routing number is the first nine-digit number on the bottom of each check.