WPF Border strange gaps
I was testing out how to use the WPF grid and borders. I noticed a small gap between adjacent borders, it doesn't always appear. I ended up finding it was related to the use of device-independent units in the WPF graphics system.
This is explained in full on the MSDN article: Pixel Snapping in WPF Applications
Setting the SnapsToDevicePixels property to true prevents the odd affects.