Make sure elements in your design line up, no matter which application you're using.

Alignment: all good design requires it, but some applications don't give you the tools do it effectively. The Guides tool allows you to align elements on your screen independently from the applications you are using.

The first thing you'll want to do after opening the tool is to create a new guide. The following methods can be used:

When you adjust a guide, you'll see a number appear—this is the guide's position in pixels measured from the top-left corner of the screen. Linked guides (which are shown by a highlighted chain icon) will move together as a group. To link the guides, select one of the guides by clicking on its move icon. Then click on the chain icon of all the guides you want link to the selected guide. To unlink, click on the chain icon again.

After you've created all of your guides, you can save them in a file for later use. There are menu options, under Guides in the menu bar, that allow you to save and open guides. When you open a file with guides, you have an option to add them to the existing ones on screen. By default, the current guides will be removed before the new guides are loaded.

If you want to simply view the horizontal and vertical guides themselves without control handles or measurement pills cluttering your view, you can turn on Simplify Interface In Background under General Preferences. This way, when xScope moves to the background, only the guide lines themselves will be displayed.

Use the Clear All Guides if you want to clear the guides manually. If you accidentally remove a guide, use ⌘Z (Undo) to get it back.

If you're lucky enough to have multiple displays attached to your Mac, make sure to check out General preference to show Guides and Frames on a single monitor. By default, guides and frames are displayed on all displays, but it can be very helpful to keep your code on one display and your measurements on another display. It's a lot easier to read your code when there aren't lines all over it :-)