<Instance ref.Class="sample::BoundsControl">
  <CustomControl>
    <Bounds AlignmentToParent="left:0 top:0 right:0 bottom:-1" PreferredMinSize="y:50">
      <SolidBorder Color="#FFFFFF"/>
    </Bounds>
    <Bounds AlignmentToParent="left:-1 top:-1 right:0 bottom:0" PreferredMinSize="x:50 y:50">
      <SolidBorder Color="#FFFFFF"/>
    </Bounds>
  </CustomControl>
</Instance>