Ordering Markers, Stroke and Fill
An object’s path determines its shape. The stroke is centered on the path, one half of it on the inside of the path, overlapping with the fill, the other half is on the outside. Markers, too, are centered on the path.
In the Order section of the Fill and Stroke dialog, you can select the order in which these different parts of an object will be drawn. This way, you can place markers (and / or strokes) above or below the fill.