DockPanel Fill
<Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Dock Panel Demo" > <DockPanel> <Button DockPanel.Dock="Top">1</Button> <Button DockPanel.Dock="Left">2</Button> <Button DockPanel.Dock="Bottom">3</Button> <Button DockPanel.Dock="Right">4</Button> <Button >5</Button> <!-- Fill --> </DockPanel> </Window>