The Braille slate and stylus are the basic tools for brailling (process of writing in Braille). The slate is a set of two hinged plates, usually made of plastic or metal. Its function is to hold the paper while the writer guides the stylus to create Braille cells that are properly aligned and consistently spaced. Smaller, portable slates have, approximately, 20 cells per line. Larger slates, required for use with 11 in. x 11 in. paper (the official paper size used in Braille documents), may have up to 40 cells per line. Braille cells consist of six holes, arranged in a three-hole by two-hole matrix. In Braille, letters and numbers are represented by cells in which some of the dots are embossed and some left blank. The back plate of the slate has shallow holes. The front plate has a series of rectangular openings, each with six indentations along its sides to guide the stylus into the corresponding shallow holes on the back plate. When the paper is placed between the plates and the stylus is pressed into it along one of these indentations, a raised dot is formed on the other side of the paper (the shallowness of the holes on the back plate avoids the perforation of the paper by the stylus). Like in printmaking, brailling is done in reverse: the punctuated sheet has to be turned around to be read: writing has to be done from right to left.
