Guidelines are non-printing extensions of rulers that can be positioned anywhere in the drawing window (Figure 9.5). They are very useful for setting up the areas where you are going to draw and for helping to align objects. Guidelines can be vertical, horizontal, or angled.
To create a horizontal guideline, click the horizontal ruler and drag down. To create a vertical guideline, click the vertical ruler and drag across.
When the guideline is in the proper position, release the mouse button.