Behind the Designer drawing area is a Grid, an invisible set of lines that can help align your objects. To see the Grid, select Show Grid from the View menu. When you draw with Use Snaps turned on, the objects in your drawing automatically align themselves with the nearest grid line. This makes it easy to get straight lines and neat arrangements.
Use Snaps in the Arrange Menu
Using the Define Rulers and Grid command under the View menu, you can choose how your objects align with the grid.
The Define Rulers and Grid dialog
To position your objects freehand, without using the grid, turn off Use Snaps under the Arrange menu.