How to change terrain shader

Hi , I wanted to use depth mask on my terrain and in this tutorial :
http://www.blog.radiator.debacle.us/2012/08/how-to-dig-holes-in-unity3d-terrains.html
it says I have to change the render queue of my terrain by changing it's shader. I saw this thread : http://forum.unity3d.com/threads/54742-How-to-override-the-terrain-shader

and it says to override terrain's shader I have to write a shader with the same identification. But what identification I should use to replace the shader?

I'll appreciate if someone can help me with this.

thanks