“Manipulatives are designed to mediate between a particular mathematical concept and the way pupils learn that concept. While historically the term “manipulative” has signified hands-on, “concrete” materials, numerous researchers have extended that definition to encompass computer manipulatives.

Cuisenaire rods are mathematical learning aids that were invented in 1945 by a Belgian primary school teacher, Georges Cuisenaire and popularized by Caleb Gattegno. They provide a hands-on way to explore mathematics and to learn such mathematical concepts as counting, the four basic arithmetical operations, working with fractions, and finding divisors. Here, we present several Web Sketchpad models of Cuisenaire rods.” (Sine of the Times). More here.