You can align objects to each other. For example, if you select three objects and align them to the center, they are stacked in the center of the bounding box.
Designer uses the bounding box that surrounds all selected objects as the basis for alignment. For example, if you select three objects and align them at top left, they align to the top left corner of the surrounding bounding box. To align objects, choose a command from the align pop-up menu. Or, you can open the Align dialog box by pressing ALT+1 (one).