Using the Addition Strip Board, the child practices the sequence of addition combinations 1–9, and begins the process of memorization of the addition tables. The material is composed of a hardboard chart 12 squares by 18 squares with the numbers 1–18 printed across the top. Stored in a hardwood box are the strips used for the exercise, 9 red strips divided into squares and 9 solid blue strips, both printed with the numerals 1–9.