BorderBrush: We can set the BorderBrush to a named color. In this example, I use a red color: Tomato.
BorderThickness: This attribute indicates the number of pixels wide the border itself is.
Alignment: We set the HorizontalAlignment and VerticalAlignment attributes to Stretch. These expand (anchor) the border to the container.
HorizontalAlignmentAlso: I changed the Margin value in the border to equal 10 on each side. We could use the value "10" as the entire margin value.
Here: We nested an "aqua" border within our "tomato" border. We use the simplified margin syntax. We set the thickness to 3.