Answer:
What breaks on the water but never on the land?
You will find me with four legs, but no hair. People ride me for hours, but I don't go anywhere without needing to be tugged. Jerked or turned on, I always manage to be ready for work.
Look into my face and I'm everybody. Scratch my back and I'm nobody.
I am the greatest teacher out of them all, but alas in the end I kill my pupils.
The higher I climb, the hotter I engage. I cannot escape from my crystal cage.
What did the piece of wood say when he saw the screwdriver and screws approaching?