There are not any leaves or sticks in the gutters we talk about at CPC. Rain does not collect in them, and birds never nest here.

A gutter in design is the space for binding between two facing pages that make up a spread. All types of books have them but how they look is very different depending on the binding.

Gutters need to be wider for perfect bound books than they do for saddle stitch because of how the pages curl into the binding. Coil-bound book gutters have to take the size of the coils into account, so they do not puncture the text or artwork.

In the below images, the margins are outlined in blue while the gutter is shaded in purple. The general recommended gutter size for books is half an inch. 

Coil Bound Book

Saddle Stitch Book

Perfect Bound Book

The term can also refer to the space between two columns on a page. Breaking longer chunks of text into smaller sections can provide more breathing room on the page and make it easier for the reader to focus. They can also be helpful on items like brochures, menus, and playbills. A designer has the responsibility of determining how wide a gutter will be right for the art. Too much space and they appear disconnected. If the gutter is too tiny then it looks scrambled and overwhelming.