I've been trying to design a simple tap to learn SolidWorks. I created the main body of the tap and a a column for the valve. I then tried to mirror only to get a disappointing "Boundary feature curves must all be closed or all be open". Here's what the Mirror tool shows when I accept it:
I've been told to ask for help here. And I've attached the file. It's possible I'm approaching this completely wrong - I'm still learning. Any criticism welcome.