Good graphic design begins with layout, and one of the key principles of design is alignment. Adobe Photoshop CS2 features a grid function you can access by going to View>Show>Grid. This feature makes perfect alignment of design elements a breeze. However, the grid in Photoshop is merely a layout tool, and it will not print with your design. Occasionally you may find you need a grid to use as an actual design element in your graphic. Fortunately there is a simple solution.
Decide the size of the squares needed in your grid. Divide the horizontal size of your grid by the number of squares desired to calculate the size of each square. For example, if your image is 1000 pixels wide and you want 10 squares across the document, each square would be 100 pixels by 100 pixels (1000/10=100).
Go to File>New and set the document size to the size of your square. Using the example in the previous step, the document size would be 100 pixels by 100 pixels.
Press Control+A to select the entire work area.
Use the down and left arrow buttons on your keyboard to move the selected area one pixel at a time. The more pixels down and to the left you move the selection, the wider the lines of your grid will be.
Go to Select>Inverse. This should make a backward L-shaped selection along the right and bottom of the square.
Select the Paint Bucket tool (G) and fill the selection with your chosen line colour.
Press Control+A again to select the entire square. Go to Edit>Define Pattern. Name the pattern "Grid."
Go to File>New and set the document size to the dimensions you want for your grid. If you've already started the image you want to apply the grid to, open that file instead.
Click the Paint Bucket tool (G) and, in the toolbar across the top of the screen, change the "Set Source for Fill" drop-down option to "Pattern." Click on the pattern swatch to open the pattern drop-down list. Select the "Grid" pattern you created previously.
Click anywhere inside your document to fill with the grid pattern.
Your grid doesn't have to be comprised of perfect squares. To create grids with rectangles, play with different document dimensions while creating patterns.