Ruler

The ruler contains several helpful tools for styling your outline. To show the ruler, select Format ‣ Text ‣ Show Ruler, or click its button in the toolbar.
The Styles pop-up menu contains some default styles, and all of your named styles. Select one of these styles to apply it to the selection in the outline.
Clicking one of the align buttons align will set the alignment for the current selection in the outline.
From the Spacing pop-up menu, you can set the distance between lines of text for the current selection in the outline. There are preset values for Single, One and a half, Double, and Triple spacing, or you can set up your own. Choosing Other... summons up a sheet with spacing controls.
With the Line Height section you can set a multiple for the line height, based on the font size. The at least and at most controls set a minimum and maximum line height specifically in points.
The Spacing section is for changing the amount of space between lines and paragraphs: the line spacing is used when text wraps to the next line, whereas the paragraph spacing is used when there's a line break.
On the far right side of the ruler is a pop-up menu that lets you change the units that the ruler uses. The available units are centimeters, inches, points, and picas.
The ruler itself changes based on your current selection. Its zero-point is based on the column and the indentation level of the selection. Symbols on the ruler such as tab stops can vary based on the selection.
By default the ruler contains regularly-spaced left tab stops, which look like right-pointing triangles tabstop. You can drag these around to rearrange them, click in an empty spot to create them, or drag them off the ruler to get rid of them. Text at left tab stops will be left-aligned to the tab stop, but there are three other types of tab stop. Text at right tab stops will be right-aligned to the stop, text at center tab stops will be centered around the stop, and text at decimal tab stops will have its decimal point aligned to the stop. To get these other types of tab stops, control-click or right-click a tab stop in the ruler for a pop-up menu. You can also option-click a tab stop to cycle through the available types.
The first line head symbol looks like a narrow horizontal rectangle firstlinehead. Each paragraph's first line will be aligned with this symbol.
The paragraph head symbol looks like a down-pointing triangle paragraphhead. Each paragraph's lines past the first one will be aligned with this symbol.
The paragraph tail symbol also looks like a down-pointing triangle paragraphhead. Text will not go past this symbol; instead it will wrap to the next line.