arranged arrangement as-figure-six-on-a-die basic blind braille-alphabet braille-character-set braille-codes braille-dots braille-font braille-punctuation cell characters chart configurations enabling French-teacher grid internationally-standardised letter-substitution Louis-Braille partially-sighted patterned patterns positioned positions raised-dots sightless six-dots tactile textured textures three-dimensional-tactile-bumps touch two-parallel-vertical-lines-of-three-dots Unicode vertical vision-impaired writing-system