@pendean : My goal is to keep part of the Blue lines except the parts that overlay with Red. That method won't do, but thank you for the trouble. 

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@maxim_k wrote:

Hi Lois,

You still can use OVERKILL command, but activate Layers option:

If you will move lines you want to leave in the drawing to the top (Draw Order -> Bring to front), then the style of topmost object will be used and you underneath objects will be removed.

 

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@maxim_k : I have tried that method, selecting Layers checkbox, but the Blue lines did not disappear as wished. Maybe I am having some bugs. Meanwhile, I have completed what I wanted manually, by redrawing over in a new layer. Very time consuming but it was the only way. I will try once more that method another day and see if it works, as it's a great command in useful situation.

Thank you