Hmm. Well I loaded up a Quake 4 SP map, airdefense1, and the entire sky and sky walls were all sky caulk. What I don't understand is how the skybox texture is painted on the sky if no skybox texture is selected for those sky brushes. I tested the sky caulk texture and it doesn't contain any kind of skybox texture, as I expected. So how is id making an actual skybox texture appear in the sky using only sky caulk? I hid the sky caulk texture to check if there was an actual skybox texture under it, but there wasn't. Any ideas?