Use Guides to Create a Layout?

If you want to get all fancy, and have Photoshop build a guide layout for your entire image (for example, you want a vertical guide every three inches across your entire image, and a horizontal guide across the center), go under the View menu and choose New Guide Layout. In the dialog that appears (seen above), enter the exact number of columns and rows you want. In this case, I wanted six columns and two rows (it actually adds two guides for each instance, with a small gutter [space] between them). To change the amount of space between each of these double-guides, lower or raise the amount in the Gutter fields. If you want just one guide, enter 0 for your gutter.