ASME Y14.100 : Engineering Drawing Practices
Those constituents of an assembly or part (such as oil, wax, solder, cement, ink, damping fluid, grease, flux, welding rod, twine, or chain) that satisfy one or more of the following criteria: the quantity required cannot readily be predetermined; the physical nature of the material is such that it is not adaptable to pictorial representation; the finished size is obtainable through use of such tools as shears, pliers, or knives, without further machining operation; and the final configuration is such that it can be described in writing without the necessity of pictorial representation.
See Also:
Assembly, Part