With DockPanel you can arrange child elements either horizontally or vertically, relative to each other.
Note: LastChildFill property: the last child element of a DockPanel always fills the remaining space!
Example:
XAML:
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525" Background="#FFF3EEEE">
<DockPanel LastChildFill="True" >
<Border Height="25" BorderBrush="Black"
BorderThickness="1" DockPanel.Dock="Top"><TextBlock Foreground="Black">Top</TextBlock>
</Border>
<Border Height="25" BorderBrush="Black" BorderThickness="1" DockPanel.Dock="Bottom">
<TextBlock Foreground="Black">Bottom</TextBlock>
</Border>
<Border Width="60" BorderBrush="Black" BorderThickness="1" DockPanel.Dock="Left">
<TextBlock Foreground="Black">Left</TextBlock>
</Border>
<Border BorderBrush="Black" BorderThickness="1">
<TextBlock Foreground="Black">Content (remaining space)</TextBlock>
</Border>
</DockPanel>
</Window>