What is an analogy for microtubules?

Microtubules have two major functions in cells and in doing so act such as a skeleton as well as like railroad tracks. Microtubules are the major structural component of the cytoskeleton in cells, which provides the cell with structure and rigidity and verifies the shape of the cell. They also serve to transport vesicles and proteins within the cytoplasm by transport proteins known as kinesins and dyneins, which act much like railroad cars.