I've done it twice. (Repost because flairing is hard.)
Just use brick or metal.
I don't know if this has already been posted, but this is a quick tip that saved my ass a couple times. Have you ever kept spectating the guy who killed you because you want to see if your trap will kill him? Well, when you're the one who gets the kill, be careful about that little eye in the bottom left corner, especially when you're in any kind of building.