<StackPanel Margin="0,19">
        <Grid Margin="76,0,7,19">
            <Grid.ColumnDefinitions>
                <ColumnDefinition/>
                <ColumnDefinition Width="Auto"/>
            </Grid.ColumnDefinitions>
            <Border CornerRadius="10,0,10,10" Background="Red" VerticalAlignment="Top" Height="60"/>
            <Polygon Fill="Red" Points="0,12 12,0 24,0 12,12" Margin="-12,0,0,0" Grid.Column="1"/>
        </Grid>

        <Grid Margin="7,0,76,19">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition/>
            </Grid.ColumnDefinitions>
            <Polygon Fill="Red" Points="0,0 12,0 24,12 12,12" Margin="0,0,-12,0"/>
            <Border CornerRadius="0,10,10,10" Background="Red" VerticalAlignment="Top" Height="60" Grid.Column="1"/>
        </Grid>
    </StackPanel>