I have a spine, but no bones. I have a tail, but no body. I witness a thousand adventures, yet I never move an inch on my own. I’m the quiet sleeper between the pages, holding your place until the story resumes. What am I?

If you don't want uninvited guests moving in with their entire stock and barrel, you need me to keep them out.

You think you've got it bad? People use me as a milestone for ugliness. In fairy tales, I'm usually some kind of curse or punishment or bad character. In a book about kid wizards, I'm the least-wanted pet. Even nature mocks me by creating a stool in my honor... that I'm too big to sit on!

I may arrive in a moment and can vanish just as fast. I weigh nothing, yet can lift a weary heart. I grow brighter when shared and dim when held too tight.

I can lock your door or dash down the street. One holds things shut, the other moves feet.