Mirror Ruler is a tool that draws the same illustration on the flip side. It is useful in producing symmetrical illustrations.
From ①the Ruler tool, select ②Mirror Ruler.
Drag ③the Phase slider left and right to change the angle.
Drag ④ to change the position.
Now, if you draw something with the center as the axis, you can see the same drawing appear on the other side.
Finished. Using the Mirror Ruler can save you time and effort in creating symmetrical illustrations.