The rekenrek was designed by Adrian Treffers, a researcher at the Freudenthal Institute in Holland. It supports the natural mathematical development of children, providing a visual model of number relationships.

The rekenrek features two rows of beads, each broken into two sets of five. Like ten frames, this tool helps students see the quantity of five as a whole and develop strategies to solve equations.

A comprehensive guide on using the rekenrek can be found at:

http://www.k-5mathteachingresources.com/Rekenrek.htm

Although rekenreks are not terribly expensive (about $6.95 apiece) and are readily available from educational supply companies, there are homemade options. One example can be found at:

http://www.k-5mathteachingresources.com/how-to-make-a-rekenrek.html