Custom border stretch

Main.xaml

<Grid
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:noesis="clr-namespace:NoesisGUIExtensions;assembly=Noesis.GUI.Extensions">
  <Border Margin="100,200">
    <Grid>
      <Grid.ColumnDefinitions>
        <ColumnDefinition Width="60"/>
        <ColumnDefinition/>
        <ColumnDefinition Width="80"/>
        <ColumnDefinition Width="10"/>
      </Grid.ColumnDefinitions>
      <Grid.RowDefinitions>
        <RowDefinition Height="100"/>
        <RowDefinition/>
        <RowDefinition Height="35"/>
        <RowDefinition Height="40"/>
      </Grid.RowDefinitions>
      <Path Grid.Column="0" Grid.Row="0" Data="M0,40L40,0 60,0 60,100 0,100z" Fill="Blue"/>
      <Rectangle Grid.Column="1" Grid.Row="0" Fill="Blue"/>
      <Path Grid.Column="2" Grid.Row="0" Data="M0,0L80,100 0,100z" Fill="Blue"/>
      <Path Grid.Column="2" Grid.Row="1" Grid.RowSpan="2" Data="M0,0L80,0 60,100 0,100z" Stretch="Fill" Fill="Blue"/>
      <Path Grid.Column="2" Grid.Row="3" Data="M0,0L60,0 30,40 0,40z" Fill="Blue"/>
      <Path Grid.Column="2" Grid.Row="3" Data="M35,40L60,5 57,26z" Fill="Blue"/>
      <Rectangle Grid.Column="1" Grid.Row="3" Fill="Blue"/>
      <Path Grid.Column="0" Grid.Row="2" Grid.RowSpan="2" Data="M0,0L60,0 60,75z" Fill="Blue"/>
      <Rectangle Grid.Column="0" Grid.Row="1" Fill="Blue"/>
      <Rectangle Grid.Column="1" Grid.Row="1" Grid.RowSpan="2" Fill="Blue"/>
    </Grid>
  </Border>
</Grid>