The Add/Cut function in the Extrude window is grayed out. How can I activate it?
Can anyone help?
That option is grayed out until you have 3D geometry in your part because obviously you can't do a cut when there's nothing there to cut from. Once you have something modeled, then you have the option to choose to do an add or cut.
I agree with Ben though the image is not visible.
Do you only have surfaces ? In that you may want to project the sketch on to the surface and trim it.
What Ben means is 3D Solid geometry is required for the Add/Cut button to be enabled.