Reading Guide products are designed to aid students and adults with the following difficulties: skipping words, skipping lines, reversing letters, transposing letters, losing your place, re-reading lines, squinting, concentration, comprehension, red/watery eyes and reading fatigue. Slowly move white slider bar in or out as you read along. Focus on words, letters, phrases. Aids in fluency and comprehension, and blocks distractions. Easily track print through transparent tinted window.