This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/hKKD0I55IWb

I designed this bracket to keep my Surface Pro 3 from folding forward or backward. Works great at keeping it stable. I don't have a Surface Pro 4, but I believe this bracket should be able to fit it as well. It holds the screen at a 120-degree angle from the keyboard. Feel free to try and improve this design!