Three knocks with no one at the door appear in many folk tales of the uncanny. Dream tradition reads them as something trying to get your attention — a thought or a feeling asking to be let in.
Where in your waking life have you met something like this lately?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.