How do I change the line weight? Under wall selection setting > cut line pen, its 1.69 mm already. But it doesn't seem to have any difference. Help please, its urgent. Thanks!
What do you mean by "doesn't seem to have any difference"? Difference where? Difference compared to what? When printed? On screen?
Changing to a different pen will normally change the thickness. You won't necessarily see a change on screen unless you have the 'true line weight' button selected in the 'on-screen view options' toolbar. You may also find you have to zoom in fairly close to the lines to see any visible change.
To change the thickness of the actual individual pens you need to edit the penset that is currently applied.
