What is the meaning of the keys which Douglas is trying to open the door?

In the context of Douglas's struggle to open the door, the keys symbolize the various attempts and tools he uses to unlock new opportunities or understand deeper truths in life. Each key represents different experiences, lessons, or insights that he believes might help him gain access to a new understanding or phase in his journey. Ultimately, the act of trying to open the door reflects the universal human quest for growth and discovery.