Most manufactured items, as well as their components, are defined by a drawing, usually
referred to as an engineering drawing. An engineering drawing shows the dimensions, tolerances,
materials, and finishes of a component. The engineering drawing will be an item on a
bill of material. An engineering drawing is shown in Figure 5.8. The bill of material (BOM) lists
the hierarchy of components, their description, and the quantity of each required to make
one unit of a product. A bill of material for a manufactured item is shown in Figure 5.9(a).
Note that subassemblies and components (lower-level items) are indented at each level to
indicate their subordinate position. An engineering drawing shows how to make one item on
the bill of material.