Canto 16

The wheel made up of the three warriors is supposed to represent the unity of the people in Hell. The people in Hell are drawn together by the common bond of being condemned to suffering by God. They don't seem to feel any genuine affection for each other because, lets face it, love isn't what sent them to Hell in the first place. However, being in the same situation makes them face the facts that they are all suffering and the only way to get rid of even a fraction of that pain is to work together. This way of joining forces can be seen in the way the men hold on to each other for support at they spin around Dante in order to talk to him as well as keep moving. A wheel is usually a part of a tool that is used to help a person go faster or to carry a heavier load (like a bike or a wheelbarrow). It is a device to make things easier, as these warriors seem to be doing for each other.