One pixel horizontal line drawn as a rectangle
<UserControl x:Class='SilverlightApplication3.MainPage' xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml' xmlns:d='http://schemas.microsoft.com/expression/blend/2008' xmlns:mc='http://schemas.openxmlformats.org/markup-compatibility/2006' mc:Ignorable='d' d:DesignWidth='640' d:DesignHeight='480'> <Canvas> <Rectangle Fill="Black" Canvas.Left="99.5" Canvas.Top="59.5" Width="301" Height="1" /> </Canvas> </UserControl>