Ahhh! Yes! Thank you very much! That helped tremendously!!

I've only been using Sketchup for about a week, so that explains why I'm already here questioning it.
Anyway, I've been trying to use the fill tool on buildings I've built in Sketchup, but every time I use the fill tool on one face of the house, it doesn't paint that face, but the one beneath it.
Why is this and how may I fix it?