How can I define a "gutter" (i.e., binding margin) in the page setup / style?

The term “gutter” is a publishing industry-specific one used to indicate:

a. Space between two pages in a form.

b. White space between the facing pages of an open book (Wikipedia).

c. Space between two columns of type.

How and where do I setup the page gutter in LibreOffice Writer?
I am trying to format pages

thanx a bunch

Software Variations

Have a look at:

This has a explanation of how to format gutters for book layouts: http://is.gd/NRiQiw it’s for OOO but the same settings are in LibreOffice. For clarification, per @oweng, A Page layout of “Mirrored” should only be used in situations where a single page style is used and needs to be flipped throughout a work i.e., fairly simple layouts. For more complex layouts requiring multiple page styles it is necessary to set the Page layout to either “Only Right” or “Only Left” i.e., the gutter (inner margin) is separately defined in each page style for the right or left margin accordingly. Here is a screenshot of the relevant dialog in LibreOffice.

@ROSt53 gutter is a generic publishing term and not a software specific term. Gutter settings are typical in most desktop publishing software like Scribus and QuarkExpress. Gutter is defined as “the blank space between facing pages of a book or between adjacent columns of type.”

I have marked this answer up, but it requires clarification. A Page layout of “Mirrored” should only be used in situations where a single page style is used and needs to be flipped throughout a work i.e., fairly simple layouts. For more complex layouts requiring multiple page styles it is necessary to set the Page layout to either “Only Right” or “Only Left” i.e., the gutter (inner margin) is separately defined in each page style for the right or left margin accordingly.

Where is the screenshot? Missing here?

“gutter” is a word not used in LibO (at least I never saw and I never missed it).

For a) you need to go Format > Page > Margins and Layout Settings.
There you can adjust the margins including what MSWord calls “gutter”. You need to consider if you have double side printing, etc

For c) the same window but select the tab “Columns”; there you find space settings between columns

For b) I am not sure what you mean. You might need to configure the 1st-Page / Title Page on not the other pages.

Help wiki is recommended for further reading: Page - LibreOffice Help

Depending how often you need to use these settings you might better to the same in Styles Window (F11) “Page” tab.

Before 7.2, you would play with the page style Page Layout Settings.

Running “universal” pages

Select Mirrored in Page layout. Margin labels change for Inner and Outer. Set accordingly.

Don’t use Right & Left.

One side only page

The layout is either Only right or Only left. Set the appropriate margin corresponding to the inner side wider than the opposite.