The knobbed cyilnder blocks are made of wood that are lightweight and that are designed to hold cylinders of various diameters and depth. They are used to help a child to discriminate between size and depth of objects he/ she touches and sees. Apart from helping a child to visually discriminate different sizes, the wooden knobs help a child in writing as well, as they learn to find the effect of gripping or pinching the cylinders to be similar to holding a pencil.

The knobbed cylinder blocks are designed in four sets. Each set consisting of different dimensions, sizes and depths. Different varieties are meant to help children differentiate better as they progress. The four variations are mentioned in the following order:

• The cylinders decrease in width, maintaining the same height.
• The cylinders decrease in height and width.
• The cylinders decrease in width and increase in height .
• The cylinders decrease in height, maintaining the same width.