defining bones

last week we animated an articulated object(one has multiple joints）
the first step to create articulated motion is to define the bones of our objects. the bone tool could be used.1. drag all these symbols to the right position
2.select the bone tool 3. click on the base of the cranearm 1' instance and drag the bone tool to the base of the cranearm 2' instance. release the mouse button. 4. the same methods in the following
5. the final one is also the most important one. rename the pose layer cranearmature and delete the empty crane layer that contain the initial movie clip instance.
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