there should be a texture in your library called AAATRIGER. if you dont have it get the zhlt.wad from somewhere. it think superjer has it hosted here. im pretty sure AAATRIGGER is basically an invisible, untouchable brush that you can apply stuff to. so, if you applied a bombsite property to and AAATRIGGER, and went into the game, you wouldnt see a giant pink thing with a's all over it, but when you step inside where the brush was in hammer, you would be inside a bombsite. same goes for buyzones.