How do I make it so that the 3D text doesn't show through objects?

I am making a warehouse and I have 3D text on the top of it. I can see the text through the walls and I do not want that.

http://wiki.unity3d.com/index.php?title=3DText

We had a similar problem making City of Steam signposts. I can’t give you the actual code we used (company IP and lawsuits and horrible things like that and all) but the trick is to modify the shader you are using (Copy it first) to handle the z-buffering correctly.

I think you will find this question and answer very helpful.
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