If the appendix is "formal," it should contain a beginning, middle, and ending. For example, if the appendix contains tables of test data, the appendix should not only contain the tabular data, but also formally introduce those tables, discuss why they have been included, and explain the unusual aspects that might confuse the reader. Because of time constraints, your instructor might allow you to include "informal" appendices with calculations and supplemental information. For such "informal" situations, having a clear beginning, middle, and ending is not necessary. However, you should still title the appendix, place a heading on each table, place a caption beneath each figure, and insert comments necessary for reader understanding. (See a sample appendix .)
As a rhetorical device, it can serve various purposes, often dependent on the relationship of the speaker to the addressee and the extent of their shared knowledge. Apophasis is rarely literal; instead, it conveys meaning through implications that may depend on this context. As an example of how meaning shifts, the English phrase "needless to say" invokes shared understanding, but its actual meaning depends on whether that understanding was really shared. The speaker is alleging that it is not necessary to say something because the addressee already knows it, but is it so? If it is, it may merely emphasize a pertinent fact. If the knowledge is weighted with history, it may be an indirect way of levying an accusation ("needless to say, because you are responsible "). If the addressee does not actually already possess the knowledge, it may be a way to condescend: the speaker suspected as much but wanted to call attention to the addressee's ignorance. Conversely, it could be a sincere and polite way to share necessary information that the addressee may or may not know without implying that the addressee is ignorant.