Letteral

[A certain effect is achieved] by a letter, by “old man R”, as the master agent is alone named[…]Thus, when Hitchcock repeats certain names and syllabic or even letteral patterns across his films, they appear to link up in active networks[…]Such repetitions isolate specific signifiers—individual letters or letteral clusters, sounds[…], visual “puns”, and citations—which may operate like monadic and nomadic switchboards whose proliferation continues to alter the afterlife not only of the film texts themselves[…]but the literary or cultural mnemonics that they have become embedded in.

Source: wiktionary

In order to avoid the character of being slovenly, always read the lines as composed. This should be done as soon as they are finished and before spacing out; in time the habit will become so fixed, that in spacing out, or even in composing the line, the eye will wander over the words, and detect any letterals.

Source: wiktionary

LITERALS type characters: to read proof for literals is to read letter for letter, watching for proper spelling, punctuation, etc., as well as for typos: formerly spelled letterals.

Source: wiktionary