Bottom borders on WPF Grid
On a Border
control You can do BorderThickness="0 0 0 1"
to only have a bottom border shown.
Top and bottom border thickness of 5, left and right border thickness of 0
BorderThickness="0 5"
Top and bottom border thickness of 0, left and right border thickness of 5
BorderThickness="5 0"
Border Thickness - Left: 1, Top: 2, Right:3, Bottom: 4
BorderThickness="1 2 3 4"
Hope this helps!