Guides are represented by lines, which appear thick when selected. To create a guide, simply drag a line from either the vertical or horizontal rulers. You can create any number of guides from both the vertical and horizontal rulers. Just like rulers, guides help in orienting different shapes of the diagram properly. You can turn of the Ruler checkbox if you need some screen estate. When you drag the shape vertically or horizontally, these 3 dotted lines help position the shape exactly at the place you need. These 3 dotted lines denote the left, middle, and right parts of the diagram.

When you move a shape, you will notice that there are 3 dotted lines (shown in the following example in red rectangles) on both the vertical and horizontal rulers. Rulers can be switched off or on with a simple checkbox in the Show section of the View tab. They help orient the shapes to attain a consistent and clean look. Rulers help in providing perspective to the elements in the diagram. The main visual aids available include rulers, grids, and guides. Visio comes with visual aids to help align and structure the elements in the diagram so that it appears great both on-screen and in print.

Adding Elements & Controls to Wireframes.

Scaling & Adding Structural Elements to a Floor Plan.

Adding Markers & Indicators to a Timeline.

Customizing Topic Shape, Style & Layout.

Breaking Down Structures Using Sync Copies.

Creating Three & Multiple-position SmartShapes.

How to change text direction in visio