What does the "Join" option do when using the Extrude function?

The "Join" option in the Extrude function is utilized to merge the newly created extruded shape with the existing geometry within the design. When you select "Join," the resultant body from the extrusion will become one continuous object with the original geometry that it intersects. This is particularly useful for building complex shapes as it allows for the creation of more intricate designs without fragmenting the overall structure into separate bodies.

This option is essential for maintaining structural integrity and ensuring that the model behaves as a singular unit during further modifications and analyses. By merging bodies, it simplifies the design and enhances the workflow in Fusion 360, as it avoids the complications associated with managing multiple separate bodies.

In contrast, creating a separate body, subtracting material, or duplicating shapes serves different functional purposes, which do not align with the intent of combining and simplifying the design using the Extrude function.