Using Grid.ColumnSpan
<UserControl x:Class='SilverlightApplication3.MainPage' xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml' xmlns:d='http://schemas.microsoft.com/expression/blend/2008' xmlns:mc='http://schemas.openxmlformats.org/markup-compatibility/2006' mc:Ignorable='d' d:DesignWidth='640' d:DesignHeight='480'> <Grid Background="Beige"> <Grid.Resources> <Style TargetType="TextBlock"> <Setter Property="Margin" Value="5,3" /> </Style> </Grid.Resources> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" /> <ColumnDefinition /> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> <RowDefinition Height="Auto" /> </Grid.RowDefinitions> <TextBlock Grid.Column="0" Grid.Row="0">A:</TextBlock> <TextBlock Grid.Column="1" Grid.Row="0">a</TextBlock> <Rectangle Grid.Row="1" Grid.ColumnSpan="2" Margin="5" Height="1" Fill="Black" /> <TextBlock Grid.Column="0" Grid.Row="2">B:</TextBlock> <TextBlock Grid.Column="1" Grid.Row="2">b</TextBlock> <TextBlock Grid.Column="0" Grid.Row="3">C:</TextBlock> <TextBlock Grid.Column="1" Grid.Row="3">c</TextBlock> <TextBlock Grid.Column="0" Grid.Row="4">D:</TextBlock> <TextBlock Grid.Column="1" Grid.Row="4">d</TextBlock> <Rectangle Grid.Row="5" Grid.ColumnSpan="2" Margin="5" Height="1" Fill="Black" /> <TextBlock Grid.Column="0" Grid.Row="6">E:</TextBlock> <TextBlock Grid.Column="1" Grid.Row="6">e</TextBlock> <TextBlock Grid.Column="0" Grid.Row="7">F:</TextBlock> <TextBlock Grid.Column="1" Grid.Row="7">f</TextBlock> </Grid> </UserControl>