What are non printing guides in desktop publishing?

Non-printing guides are special lines or marks that are used to help position and align elements on a page, but they do not appear on the final printed document. These guides are often used to ensure that text columns or graphics are positioned accurately, or to ensure that elements are evenly spaced on the page. Non-printing guides can be found in most desktop publishing applications, and can typically be turned on or off as needed.

Some common types of non-printing guides include:

- Margin guides: These lines indicate the edges of the printable area on the page, and can be used to ensure that content is not too close to the edge of the paper.

- Text column guides: These vertical lines can be used to mark the boundaries of different columns of text on a page.

- Center line: This horizontal line runs down the center of the page and can be used to aid in aligning center-aligned text or graphics.

- Grid lines: These lines create a grid of evenly spaced horizontal and vertical lines that can be used to align multiple elements accurately.

- Baseline guidelines: These are fine, evenly spaced horizontal lines that help you align the baselines of type, which improves vertical alignment and helps text blocks be easy to read.

Overall, non-printing guides provide designers with an important tool for accurately laying out and aligning various elements within a desktop publishing project, improving its visual aesthetic and ensuring a professional-looking document.