All you wanted to know, but never dared to ask about Carbon Rigid "bodies"!

Carbon is built on a next generation dynamics architecture where there is no explicit notion of soft bodies or rigid bodies.

There are actuators:
Carbon Rigid
Carbon Actor
Carbon Soft
which are dynamic objects that can be constrained.

Then there is a Carbon Shape, which can either be solid or deformable and is defined through a mesh with fatness / thickness properties.

And there is a Carbon Body, which is a true collision entity, based on the relationship between an actuator and a shape.

Check out the new User Guide entry in the docs for full description of these concepts - applicable to Carbon in Houdini or Maya.
Carbon for Maya docs

We also provide a macro in Carbon for Maya, to generate composite Carbon objects  = Rigid "bodies".
This tutorial explains more about setting up a a chain link belt.

This tutorial explains more about Carbon Rigid mass boxes

This forum entry explains how to move a Carbon Rigid Body from one mesh to another

There are also several other forum entries with scripts to assist editing Carbon Rigid "bodies" here

Finally you will find various downloadable examples using Carbon Rigid "bodies" in the documentation here for Maya here