The Duo reading ruler is made of a combination of opaque and transparent plastic that both underlines the text and highlights it in a coloured tint. Simply read the text through either of the tinted plastic strips of your selected colour, and track down the page: broad strip for paragraphs; narrow strip for single lines.
DUO WINDOW READING RULERS are divided into a narrow reading window and a wide reading window by an opaque strip. People who have difficulties keeping their focus on the line being read find this design useful. Focus can be further confined by taping paper over the wide transparent window a quarter of an inch below the opaque part of the ruler, so that all words except the present line are completely blocked out.