Tomo was based on the 'soko tenboku,' a kind of character tracing method where a piece of paper was put on a work to be copied, only outlines of characters were traced with thin lines, and then areas enclosed by the lines were colored in black.
これは「双鉤填墨」という方法を用いるもので、まず写したい作品の上に紙をかぶせ、文字の輪郭だけを細く写し取り、その上で中を黒く塗りつぶすという一種のなぞり書きであった。