That's a good trick that I hadn't thought about - I guess it relies on the model allowing you to do that though, e.g. if it's a large one-piece figure you could do that for one "bodypart" at a time, which might not allow one to make a specific wall invisible.  Although I suppose you could get the same effect by using the Group Editor and grabbing all of the vertices on that wall, and then giving them a material group and making the material group transparent.

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