Sometimes, it may be the case that you want to set up a new font in the guidelines, but not make the font block visible to your viewers.
To do this, you will:
Create a new page set to "Unpublish" mode - this will ensure the page does not show to viewers.
Follow the steps laid out in this article to set up a new font in a font block on that unpublished page.
For example, it could look like this:
This will ensure that the font is usable in guideline design settings, but only visible to editors of your guideline.