A very new and exciting feature of Fusion 360, is the ability to now be able to “Edit In Place” when it comes to assemblies.  Other modelers (like Solidoworks) have had this feature for years.  It was a very pleasant surprise to see that now Fusion has it also!  To use it, you will need the latest update.  Take a look at the video below, where we will use this new feature, to perfectly conform the Archtop Neck Extension to the top!  Video also describes the feature, how to enable it, and obviously how to use it.  Hope you find this helpful!