Danny Hamilton,
You wrote above: "Private key can be used to sign bitcoin transactions" - HOW, manually? Or the wallet does it for you?

On my KeepKey, there is a PHYSICAL BUTTON that I have to press to confirm each SEND transaction.
Nowhere in Chrome KeepKey client do I see a field where I need to enter my private key manually!

Am I understanding it correctly that KeepKey (or ANY "cold" wallet) uses private key IN THE BACKGROUND to sign transactions when I press that button?