A bolt slid across a door is read as the wish for security and firm boundaries. Folk readings see it as shutting something out, or as keeping something precious in.
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.