To mirror and element with the mirror tool:
Select
Mirrorin the toolbar. Alternatively you can use shortcutShift+MIf you do not currently have an element selected, select the element you wish to mirror. If you already have 1 or more elements selected continue to step 3.
Click to place the first point of the mirror line. If you wish to create a mirrored copy, hold down
Alt/Optionbefore placing the first point of the mirror line.Click to place second point of the mirror line. The selected element will be mirrored across the mirror line.

