A great deal of the Siddham written in Japan was never meant to be read as a text. It stands on wood and on stone, in the open, in places where the audience is the passer-by rather than the scholar. The sotoba is the clearest case: a tall thin wooden tablet, notched at the top into five sections, set up behind a grave. The notches represent the five elements and the syllables written down the board are the Siddham seed syllables that go with them, so the tablet is a stupa reduced to a plank and a letter for each of its tiers.
Stone gives the same scheme its permanent form in the gorinto, a five-tiered pagoda of cube, sphere, pyramid, half-moon and jewel, each tier carrying its syllable. Grave markers, boundary stones, memorial pillars and the small figures set at roadsides all carry Siddham of this kind, usually one syllable standing for a figure or an element rather than a sentence.
That use has a consequence worth naming. Siddham is a public script in Japan in a way it never was in India, visible in ordinary places to people who cannot read it and do not expect to. What it communicates in that setting is not the sense of a word but the fact of a dedication, which is a real function and not a failed one. The letters are doing the work of a sign rather than the work of writing.