The Bone tool is used to create an armature to connect and animate separate symbol instances. It is a direct way of controlling elements that are supposed to be animated in a sort of chain reaction like the movement of limbs. This recipe gives you the run down on how to get started with the tool.
You start out by figuring out what is going to be the trunk of your armature and then connect the branches to it. The trunk is fairly stationary (like a tree trunk) and the branches, or limbs, move.
You can use the bonetool.fla file in the Chapter 9 folder. If you are already comfortable with this sort of animation, or are an intermediate Flash user, create your own file. In order for the Bone tool to work, each piece to be animated should be a symbol instance. You can take a look at bonetool_done.fla to see an example of an animation done with the Bone tool.