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Step 1: Important! In Rhino or other modeling program, delete/remove or place on a separate layer all redundant construction items so they are not accidentally exported. Depending on your personal style of modeling, there might be a lot of extra surfaces hiding throughout. This should be a familiar process for submitting final drawings:
Step 2: In Rhino, select all final objects of your model and File -> Export Selected -> "Motion Builder (*.fbx)"