The door was open, as he had kept the key in his pocket.

It might be best for you to keep the key in your pocket.

He smiled and kept the key in front of her.

You did not keep the key and the lock in the same place.

But you can find out where she keeps the key.

Where did you usually keep the key, by the way?

But in both cases you're keeping the key to yourself.

"Yeah, but you can keep the key to my apartment."

He kept the only key and straightened the room himself.

But I kept the key on a chain round my neck.