Answer:
You fill it and it empties, A metaphor for plenty, Depending on what half you see, It's either full or empty
Lots of them make up a word, And lots of words are in them. It's easy when you think about it. A while ago we stamped and mailed them.
These are believed to be found at the end of rainbows
Cold head and feetอพ Round as a ballอพ Always turning around itself.
What has 4 fingers and a thumb, but is not living?
I build up castles. I tear down mountains. I make some men blind. I help others to see.