In this chapter, we wish to calculate the structure of the region in the Sun where convection dominates the transport of energy. As in Chapter 5, we will not discuss the origin of the energy which is ﬂowing through the convection zone. Instead, we again accept the total luminosity (or ﬂux) of the Sun as a boundary condition, and seek to determine how the material arranges itself so as to “handle” the energy which is passing through. We will examine the forces which act on the medium, and determine how the medium responds. In this sense, the model we will derive is better referred to as a mechanical model rather than a complete model.