Gardiner's Sign List is a list of common Egyptian hieroglyphs compiled by Sir Alan Gardiner. It is considered a standard reference in the study of ancient Egyptian hieroglyphs. Gardiner lists only the common forms of Egyptian hieroglyphs, but he includes extensive subcategories, and also both vertical and horizontal forms for many hieroglyphs. He includes size-variation forms to aid with the reading of hieroglyphs in running blocks of text. In contrast, for example, the Budge Reference has about 1,000 hieroglyphs listed in 50 pages, but with no size variations. Gardiner does not cross-index signs; once put on the list, other significant uses may be overlooked. One example of this is G16, nbtỉ, the ideogram for the Two Ladies, goddesses Wadjet as the cobra and Nekhbet as the white vulture. These are the protective and patron goddesses of the separate Egyptian kingdoms that joined into ancient Egypt, who were both then displayed on the uraeus of Wadjet when the unification occurred and afterward considered jointly to be the protectors of Egypt and the pharaohs. This ideogram is listed only in the bird list (G), and overlooked on the deity list (C) and the reptile list (I). Other subcategories included by Gardiner are abbreviations and personalized forms, and also a complete subset, used on papyrus, specifically for the Book of the Dead. Categories A. Man and his occupations 56 signs in Gardiner (1957:242–247), with A59 "man threatening with stick" inserted after A25 "man striking with left hand hanging behind back", and two variants A14* "blood interpreted as ax" of A14 "man with blood streaming from his head"; and A17* "child sitting with arms hanging down" of A17 "child sitting with hand to mouth". B. Woman and her occupations 7 signs in Gardiner (1957:448). C. Anthropomorphic deities 11 signs in Gardiner (1957:448f.) with the addition of five 19th Dynasty signs, C12 Amun, C17 Mont, C18 Tjanen, C19 and C20 Ptah. D. Parts of the human body Expected quantity: 63 E. Mammals Expected quantity: 34 F. Parts of mammals Expected quantity: 52 G. Birds Expected quantity: 54 H. Parts of birds Expected quantity: 8 I. Amphibious animals, reptiles, etc. 15 signs in Gardiner (1957:475f). K. Fish and parts of fish Expected quantity: 7 L. Invertebrates and lesser animals Expected quantity: 7 M. Trees and plants 44 signs in Gardiner (1957:478–484). N. Sky, earth, water 42 signs in Gardiner (1957:485–492). N3 is an Old Kingdom variant