Growth cha is a visible display of the child's physical growth and development. The WHO prototype growth cha has 2 reference curves. The upper reference curve represents the median (50th percentile) for boys (slightly higher than that of girls), and the lower reference curve the 3rd percentile for girls (slightly lower than that for boys). The cha can be used for both sexes. The space between the two growth curves has been called 'road-to-health'. It is the direction of growth that is more impoant than the position of dots on the line. It used as an educational tool for mothers. Ref: Park's Textbook of Social and Preventive Medicine, 19th edition, Page 435-437.