Remembering is a curious thing. Many past events immediately come-to-mind, others are recalled after a brief mental search, while still others remain elusive. These tease the mind with the implication that the memory still exists somewhere.
The ability or inability to recall memories is illustrated with the insertions of zippers into these landscapes. Zippers can be opened to reveal something or closed to cover something up. Zippers also can convey a relationship by connecting two things or by separating them.