Montessori Language Materials Lower Case Sandpaper Double Letters Print With Box Set of 16 sandpaper letter combinations on green wooden boards: ai, ar, au, ch, ee, er, ie, oa, oo, or, ou, oy, qu, sh, th, ue. Beautiful tactile material to teach phonemes to children . Perfectly cute and very well made! The purpose of this product is to develop a muscular impression of the letter shapes and to associate the sounds with the shapes. This also helps to develop a visual impression and to learn the writing direction of the letter shapes. The Double Sandpaper Letters guide the hand for writing as the child traces the letter shapes in the style and direction that they are written. Each Double Sandpaper Letter is in lower case on boards painted green. Each board has a space on the left and right for the child to steady it with one hand while tracing the letter with the other.