I can be clean. I can be dirty. You may want to use me at your own risk. However, if you brave the nasty, you will be relieved at the end. What am I?

I have a long arm but no muscles, and I can throw things further than any athlete. I was born in ancient times to knock down walls, yet I never use a hammer. I’m not a plane, but I can make things fly; I’m not a feline, but my name starts with a cat. What am I?

I'm screwed to the wall to hold up a shelf. After all, I can't hold the books all by myself.

Four wheels, wood I boast, Concrete waves my metal friend, Balance, then I roll.

This word holds meaning even when letters are removed - but only one at a time. Full, it is a place to rest. With the second removed, it is how you rest. With the last removed, it becomes somewhere traversed yet not fully explored.