Two identical glass panes guard a display case. From outside one can see inside, and from inside one can see everything outside. They are like two identical jester sisters who always stay together and go wherever they are led; everyone brushes against them and treats them well, and they always bear the weight of all those who buy them. I am neither snail nor mushroom - water makes me come out; when it rains I get all wet, and when the sun is out I am parched. Can you guess what it is that is not a stick and not ink but one wears it and it has a stick and has ink? It sticks its head through a hole, and its family is immense. It has no arms