How do I set something as a baseline?

There are two ways to set a stock (or any other line in a chart) as a baseline by which others are measured. One way is to simply click its name in the Chart’s legend. Click it again to undo this setting. Or, if the item is listed in the ‘Compare’ menu, you can click the small graph button next to the ‘X.’ For screenshots of these actions, see the charting help documentation.