The importance of rulers and guides has grown considerably in the last few revisions of Photoshop. Guides are user-defined alignment lines. The grid is an underlying matrix of lines you can use for general alignment of all items on the page. The enhanced type features have made text-alignment issues much easier to address. In addition, designers are creating complete Web pages in Photoshop and ImageReady, which necessitates using guides and grids to maintain spacing and alignment.
Set Rulers Preferences
Choose Edit, Preferences, Units & Rulers to open the Preferences box to the Units & Rulers page. From the Units drop-down list, choose the desired unit of measurement and click OK. In this instance, you do not have to restart Photoshop for the preference change to take effect.
Choose View, Rulers to make the rulers visible around the top and left edges of the image area.
Set Guides Preferences
Choose Edit, Preferences, Guides, Grid & Slices to open the Preferences box to the Guides, Grid & Slices page. Here you can specify the color and format of the guide and gridlines, as well as the spacing for the grid. Click the color swatches to select a custom color, or use the Color drop-down lists to select from preset colors. You can also select slice colors and toggle slice numbers on and off.
Create and Activate Guides
To create a guide, click the Move tool in the toolbox. Click in the ruler area and drag into the image area. A vertical or horizontal guide will follow the tool, depending on which ruler you started with. You can drag out as many guides as you need. You can also place a guide in a specific place by selecting View, New Guide and entering the orientation and pixel position in the dialog box that appears.
Set Snap-To Parameters
To precisely align elements to guides and grids as you drag the elements, choose View, Snap To, Guides or View, Snap To, Grid. Choose these commands again to turn them off.
Lock Guides as Needed
To lock the guides in place, choose View, Lock Guides. When you lock the guide lines, you prevent them from moving accidentally, especially when you are using numerous guides.
When working with a Web design, set the ruler increments to pixels on the Units & Rulers page of the Preferences box. Then scroll the image against the rulers to take rough measurements of page elements. An alternative way to make quick measurements is to use the Measure tool to measure areas within your images.
Using Guides for Precise Text Alignment
When positioning multiple text elements or multiple lines of type, use the guides feature to ensure precise alignment.