Tape halfway point of the chain?

[Warrenkicker]

There could be reasons to need to know where the previous spot was. Say it was 4th and 18. A passes the ball and there is DPI. However the ball is still caught and A threatens the line-to-gain. A's coach wants a measurement to determine if the play made the first down. If it did then he will decline the penalty and take the play, but otherwise he wants the DPI and the automatic first down. There is a difference of three yards there that he wants if he can get them. This is the reason you don't move the box to the end of the stakes. If you really need to know where the front stake was just put your bean bag there and pick it up after measuring.