How do I duplicate a shape in HTML5's canvas?

I have a semi-complex and horizontally symmetrical shape I am trying to build using HTML5. While I was trying to finish it I realized it would be easier if I could just duplicate half of the shape, mirror it and move it to join the two images together. I'm finding examples of how to mirror and move a shape, but not on how to duplicate it.I have a semi-complex and horizontally symmetri