Slate and stylus
The slate and stylus are tools used by blind people to write text that they can read without assistance.[1][2] Invented by Charles Barbier as the tool for writing letters that could be read by touch,[3] 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.
Not to be confused with the wax tablet and stylus.Design[edit]
The basic design of the slate consists of two pieces of metal, plastic or wood fastened together with a hinge at one side.[1][4]
The back part of the slate is solid with slight depressions spaced in braille cells of six dots each. The depressions are approximately 0.75 mm (0.030 in) deep and about 1.5 mm (0.059 in) in diameter. The horizontal and vertical spacing between dots within a cell is approximately 2.5 mm (0.098 in), while the distance between adjacent cells is about 4 mm (0.16 in).[4][5][6]
The front of the slate consists of rectangular windows that fit over the braille cells in the back. The inner rim of each window is provided with six indentations, which assist the user to position the stylus properly and press to form a dot.[4]
There are pins or posts in the back of the slate positioned in non-cell areas to hold the paper in place and keep the top properly positioned over the back. The pins align with matching depressions on the opposite side of the slate. A slate as designed for a normal 8.5 inch piece of paper has 28 cells in each row. The rows can be any number, usually at least four.[4]
The stylus is a short blunted awl with a handle to fit comfortably the hand of the user.
Writing[edit]
Writing is accomplished by placing a piece of heavy paper in the slate, aligning it correctly and closing the slate. The pins in the back of the slate puncture or pinch the paper securely between the two halves of the slate.[1][4]
The person writing begins in the upper right, each combination of dots in the cell has to be completed backward. The awl is positioned and pressed to form a depression in the paper. The writer moves to one of the other dots in the cell or to the next cell as appropriate.[7]
The slate is repositioned as needed to continue writing on the paper. When completed the writer removes the slate and turns the paper over to read the braille by feeling the dots that were pushed up from the back.[4]