Be secret. So you're saying that's what the dog's guarding? That's what Snape wants.

For the entrance to this cave is guarded by a creature so foul so cruel that no man yet has fought with it and lived

Shouldn't you be guarding some Donuts and coffee right about now?

That's top secret, that is. But Hagrid, whatever fluffies guarding, Snape's trying to steal it.

That's what Sophie's guarding on the third floor. That's what's under the trapdoor, the sorcerer's stone.

Yes, there are three. It was standing on a trap door, which means it wasn't there by accident. It's guarding something.