Like the appendix in a human body, an appendix contains information that is supplementary and not strictly necessary to the main body of the writing. An appendix may include a reference section for the reader, a summary of the raw data or extra details on the method behind the work. You may be required to write an appendix for school or you may decide to write an appendix for a personal project you are working on. You should start by collecting content for the appendix and by formatting the appendix properly. You should then polish the appendix so it is accessible, useful, and engaging for your reader.