A tap controls the flow, so dream books read it as how freely feelings or resources come through. Turned on, it stands for openness; one that will not close, for something hard to stop.
Has this come up in your dreams before? What was going on in your life then?
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.