This section is from the book "The Manufacture Of Boots And Shoes: Being A Modern Treatise Of All The Processes Of Making And Manufacturing Footgear", by F. Y. Golding. Also available from Amazon: The Manufacture Of Boots And Shoes.
The size, shape, quality, and substance of the skin determines its value for a specific purpose. The position or absence of flaws, fleshcuts, and stretchiness also influence the selection. Square skins, i.e. when the length is nearly the same as the width, are usually more profitable in cutting than long narrow skins. Long skins have long necks, narrow prime leather area, thick necks, and heavy bellies. The squarer variety are shorter in the neck, broad in the butt and rib portion, giving a large prime cutting area with a small proportion of offal. Skins unequal in substance are not so valuable as those possessing uniformity of thickness. A well-grown skin is wider in proportion to its length, has a small amount of offal, is free from growth marks, is level in substance over the butt; the shank and offal is light and is well rounded. A skin that is thick in the neck and veiny usually falls away at the shoulder, has thick, awkward offal, and does not present the same cutting advantages as one level in the neck and shoulder. Fig. 160 shows a diagram of a male skin that has veiny necks, and is coarser in texture than the female skin shown in Fig. 161. This latter diagram also shows the usual division of the skin. The portion A (Fig. 161) is the butt, and is generally the stoutest and best part. It is used for the portions of boots and shoes that experience the most strain, such as vamps. B is the ribs, and is in quality the best portion of the skin, being equal to, if not better than, the butt. C is the shoulder, which is fine in texture but lighter than the ribs. It is used for parts of boots that demand light but firm, strong material. D is the neck which is often veiny and stout, especially in the male skin (see Fig. 160). E is the belly, which is less firm than the shoulder. It is stretchy as a rule. F is the flank, which is soft, loose, and flabby. H is the shank, which is light and fairly firm. The backbone is shown in Fig. 160 by A, which is usually thin and weak, and should be avoided as much as possible, especially in calf-skins.