Even the simplest drawing can contain overlapping objects, so you need control over the order in which objects appear in the drawing.
To bring an object (or selection of objects) to the front of a drawing, right-click and select the To Front command (also available from the Format menu).
To send an object (or selection of objects) to the back of a drawing, right-click and select the To Back command (also available from the Format menu).
See also: