Use fill rules
When you fill a compound path in which the subpaths overlap, or a path in which a single path crosses itself several times, you can control how Microsoft Expression Design determines which parts of the path should be filled. For example, if you draw two circles, overlap them slightly, and then combine them into a compound path, the center area (where they overlap) is considered either inside the object (and therefore filled) or outside the object (not filled). This control is called a fill rule.
Technically, fill rules are based on a winding number count. To determine whether a particular point is considered inside or outside a path, count the number of times that point is encircled by the path, with each clockwise turn canceling out a counterclockwise turn. (The path direction is typically based on the order in which you drew its points, and reversing a path's direction affects the fill rule.)
To apply a fill rule
Select an object.
In the Properties panel, in the Appearance category, click the Show advanced properties icon ) to display the Object category.
In the Fill Rule list, select one of the following:
Winding Rule Every space with a nonzero winding number is filled.
Even-Odd rule Only spaces with an odd winding number are filled.
Applying the Even-Odd Rule (left) versus the Winding Rule (right)