James Murray's "Cutline JM10" library part is a free download from bimcomponents.com (accessed directly in the objects settings dialog) and is 'as-is'. It's not a Graphisoft library part.
I just tried it and was surprised to see that enabling the mask does not display the mask any longer - tried in AC 16. It had worked in AC 10, for which it was designed. Looked at the code and the problem didn't jump out at me.
I've been using a
different break-line object by David Larrew and recommend it. It is a free download from David's site here:
http://www.archisolutions.com/store/GDL-2D_note.html
There is another cutline object that is public that also masks correctly, written by Nando Magollon. You can find it here:
http://archicad-talk.graphisoft.com/object_depository.php
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