/vr/ - Retro Games

So I'm making my first wad, getting the hang of the map editor and such and I have one real problem. I can not get the hang of textures. Obviously here I dont want the door texture to go the roof, but when you set the door you have to make the ceiling the the floor size. So how do you set how high the door goes? Also is it possible to set a texture in the middle of a wall, and have a lower and higher texture? Any and all texture tips are appreciated.