To be able to associate a processing error clearly with an upper or a lower "third fold", the printed products are marked. For this purpose there is a knife on the middle deflecting cam of the splitting device for marking the product, which cuts a small slit in the following edge of every second printed product.
But don`t you worry: This slit is so small, that it is contained completely in the paper which will later be trimmed, long after it has served its product marking purpose.