Stretched GridSplitter
<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"> <Grid Height="100" Width="400"> <Grid.ColumnDefinitions> <ColumnDefinition Width="1*" /> <ColumnDefinition Width="6" /> <ColumnDefinition Width="2*" /> </Grid.ColumnDefinitions> <Ellipse Grid.Column="0" Fill="Red" /> <GridSplitter Grid.Column="1" HorizontalAlignment="Stretch" /> <Ellipse Grid.Column="2" Fill="Blue" /> </Grid> </Page>