ufacture would be classified on the
basis of shoemaking, because that instrument would be
incapable of other use, while an instrument peculiarly
adapted to drive nails would be classified on the basis of
nailing, whether for nailing shoe-heels or other objects,
and a hammer would be classified on the basis of its
function as an impact tool even though described as for
driving nails, and even into shoe-heels.

(3) Structures (passive instruments) will, in general, be classified on
the basis of structure, either of special or general application, the
essential functions and effects of static structures being resistive or
the maintaining of forces in equilibrium.

Example: A structure recognized as peculiar to barriers of
the kind known as fences would be classified in the special
class of Fences, but posts, joints, beams, etc., recognized
as having use in general building, even though described as
used in fences, would be classified in a more general
building class, such as Wooden Buildings or Metallic
Building Structures.

(4) Compositions of matter and manufactured or formed stock or
materials will be classified in accordance with the inherent character
of the substance or material where possible, otherwise according to
special use.

Example: A pure chemical is expected to be classified on
the basis of its chemical structure and constituents, even
though useful as a food, medicine, dyestuff, explosive,
etc., and alloys on the basis of metallic composition, even
though used for bearings, coins, tools, etc.; whereas a
physical composition having no reason for existence except
to function as a cleansing composition or a paint might
have to be classified on the basis of its function as a
detergent or a coating composition, respectively. Also a
bimetallic layered foil, plate, or wire would be expected
to be classified as metal stock even though designed for
use for dental filler, plowshare, or electric conductor,
and a woven textile fabric as a fabric even though
described as used for a filter or apron for a paper-making
machine.

DIVISION AND ARRANGEMENT.

(5) The divisions or subclasses of a class should be made exhaustive,
i. e., they should be susceptible of receiving any future invention that
may fall within the scope of the class. The rule as usually phrased is:
"The constituent species must be equal, when added together