堅固

坚 = 収 + 土 : Joan of Arc (ji) built a strong (坚) and sturdy (坚) burrow out of dirt (土) in front of the anthill (an1). She even equipped it with a strong (坚) radio (収) to keep contact with her troops.

固 = 古 + 囗 : Gitta Giraffe is building a hard and solid stronghold inside the bathroom's space station. The stronghold consists of a cloister inside a wooden box.