Use ruler guides
While the page grid is a good way to align objects quickly, you might find it easier to add a single straight guide line as a visual reference (or to snap objects to it).
To add a ruler guide to your document
In the document window, use your mouse to drag a new ruler guide from either the horizontal or vertical ruler.
When the ruler guide is where you want it, release the mouse button.
To show or hide ruler guides
On the View menu, point to Show, and then click Guides, or press CTRL+; (semi-colon).
Ruler guides extend past the artboard all the way to the edge of the workspace. However, unlike the page grid, if you rotate the document window, the ruler guides also rotate.
To move a ruler guide to a new location
Hold down the ALT key when dragging the ruler guide.
To delete a ruler guide
Select the ruler guide, hold down the ALT key, and drag the ruler guide back to the ruler or outside the document window.