Why is a raven like a writing desk?

"Have you guessed the riddle yet?" the Hatter said, turning to Alice again.
"No, I give it up," Alice replied. "What's the answer?"
"I haven't the slightest idea," said the Hatter.
"Nor I," said the March Hare.
Alice sighed wearily. "I think you might do something better with the time," she said, "than wasting it in asking riddles that have no answer?"

Well, I understand that there is no answer, as it is complete nonsense, but I have came up with:
Neither are made of aluminium,
and... You cannot ride either like a bicycle.....
They work out, but they're hardly answers to riddles. :)