Inform visitors and send them in the right direction. Indoor changeable letter directories have a  felt surface. Letters fit into place neatly on the black surface of each board.The felt boards feature a grooved surface that accepts pin-style characters. .The anodized aluminum casing has full-length hinged doors with solid disc tumbler locks and shatterproof, clear acrylic doors. For indoor use. Felt-Includes 318 white 34" (19mm) Helvetica characters.