View - Snap to Grid

Select Snap to Grid from the View menu to display the Snap to Grid dialog, in which you can enable (and customize) an invisible drawing grid to help you align drawn objects (e.g., lines, rectangles, inserted graphics or text objects).

By default, the object is pulled into alignment with the nearest intersection of gridlines (as if the resolution of the screen were "decreased"). This is the snap-to-grid effect.

The display of the alignment grid itself in the graph can be toggled on and off by pressing CTRL+G, or selecting Alignment Grid from the View menu.