Changing the line thickness of a symbol in a diagram
When you change the line thickness of a symbol, you change the thickness of the line around the symbol or, if the symbol has a frame, the thickness of the frame.
1.Select the symbol.
2.Choose Effect>Line Thickness, then choose the line thickness from the sub-menu.
On the Formatting toolbar, click the up or down arrow on the Line Thickness button to increase or decrease the line thickness.