Eratosthenes Panels was a mechanical device for finding means between two extremes. This is an interactive simulation of the method Eratosthenes used to find two lines, and , whose lengths were between the lengths of two given lines, and , and such that . From this it is easy to show that which reduces to or . In our model and and this becomes . For the cube duplication problem and . To use the model: Choose a Number and a Panel Width. Then drag until length . Lines and will be the two means between and with is the required line.