Slate and stylus

The slate and stylus are tools used by blind persons to write text that they can read without assistance. Invented by Charles Barbier as the tool for writing night writing, the slate and stylus allow for a quick, easy, convenient and constant method of making embossed printing for Braille character encoding. Prior methods of making raised printing for the blind required a movable type printing press.

Design

The basic design of the slate consists of two pieces of metal, plastic or wood fastened together with a hinge at one side.

The back of the slate is solid with slight depressions spaced in braille cells of six raised dots arranged in a grid of two dots horizontally by three dots vertically. In the shape of an inverted braille dot of approximately 1.5 mm (0.059 in) diameter; .75 mm (0.030 in) depth or height; the horizontal and vertical spacing between dot centers within a braille cell is approximately 2.5 mm (0.098 in) cell to cell (dot 1 center to dot 1 center horizontally) 6.5 mm (0.26 in).