 Fitch’s method, like Jaśkowski’s, is graphical and involves a method of indicating Jaśkowski’s boxes and suppositions. The rules are of two types: those that refer to previous lines but have the new formula within the same box as the previous lines, and those that allow a box to be ended, with the new formula in the next outer box. But rather than drawing an entire box, the Fitch method uses just the left side of the box, and rather than suppositions being merely the first line of a new box, the Fitch method indicates them by entering them just above a short horizontal line.