Once you've established a baseline grid, you can force your paragraphs to align to it by choosing All Lines. This option can be applied as part of a paragraph style definition, or can be applied locally using the Control palette.
Using a baseline grid is like setting a tempo for your document. In documents that use a variety of type and leading sizes, it's perfectly acceptable to go against that rhythm by coming off the grid with certain elements, such as headings and subheads, as long as the next passage of body text finds the beat again, and reestablishes the rhythm.
Figure 16.7. Align to Grid is usually applied as part of a paragraph style definition (top), but can also be applied locally using the Paragraph Formats level of the Control palette (bottom).
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Aligning to the grid always means the next grid increment, causing leading values to be rounded up, never down. For example, if a paragraph with a specified leading value of 13 points is aligned to a 12-point grid, its leading will become 24 points.
For this reason, All Lines should be used only for body text and paragraph styles where the leading is already the same as the baseline grid increment.
When resizing graphics, the picture frame will snap to the baseline grid, making it easier to crop your picture frames to a leading increment. If you are using text wraps, set the text wrap offset to your leading increment.
If you've done the math right, choosing Align to Grid isn't strictly necessary. Your type will better align to the grid through careful planning and gentle persuasion than by coercion, because the total paragraph spacing applied to all your paragraphs is a multiple of your baseline grid increment. In practice, you'll probably find you need to add or subtract a bit of paragraph spacing here and there; this way, you, not InDesign, decide where the space is added or subtracted. The formula is simple: Total paragraph spacing (Leading + Space Before + Space After) must equal your leading increment or a multiple of your leading increment.
Let's say you're using a 12-point baseline grid and your body text is 10/12. The subheads are 18/18, making them 6 points off the grid. To put the subheads back on the grid, add 6 points of space before the subhead. Alternatively, you can add 4 points of space before and 2 points after.
First Line Only is useful for paragraphs such as multiline subheads or intro paragraphs that, because of their size and leading values, cannot keep to the grid. Nevertheless, you'll want to make sure that the first lines of such paragraphs align with the body text in adjacent columns. Subsequent lines will follow the specified leading increment.
Figure 16.8. The intro paragraph on the left aligns to First Line Only; the text on the right is set to All Lines.