(8) Up to this point, more or less cursory attention may be given individual patents; but when an arrangement of subclasses shall have been tentatively adopted it will be necessary to consider each patent carefully to ascertain whether it is properly placed.
(9) Patents that, considered as an entirety, cover means not peculiar to the class or subject-matter being revised, should, in general, when assembled in groups as indicated, have a note attached indicating not only want of limitation to the subject-matter of the class but also a more appropriate class to receive them if such there be. Although a very large proportion of patents can be accurately classified as indicated by their titles and stated uses, the mere fact that in a patent found in a class the invention is called in the specification or claims by a name peculiar to the class is not of itself a reason for considering it peculiar to the class. A gas and liquid contact apparatus may be called a heater, a cooler, a gas-washer, a water-carbonator, a condenser, a disinfecter, an air-moistener, and so on, depending upon accident of use. If there are not elements in some claim to confine the means described distinctively to what it is called, or if there are no functions necessarily implied in the means claimed peculiar to the named use, the patent should not be kept in the class unless there is no other class in the office that can receive it.
Example: Where the matter claimed is a metal beam of peculiar cross-section, it should be classified with other metal beams, as in Class 189, Metallic Building Structures, even if it is named in the application as a beam of particular use, as a railroad-tie, car-sill, bridge-tie, etc. Should a mere dash-pot be found classified in Class 171, Electricity, Generation, a note should be attached indicating that it belongs in the appropriate element class.
(10) In giving this final careful attention to the patents, each should also be scanned to see whether it contains matter that should be cross-referenced. A few lines obscurely located in a specification may contain a disclosure of a most valuable invention. No class can be deemed complete until the disclosures appropriate to it found as parts of more complex inventions in other classes, or disclosures of analogous matter in other classes, are either cross-referenced into it or cross search-notes made.
(11) To indicate cross-references, from one subclass to another within the class or from the class under consideration into another class, attach a small slip of paper to the patent and mark on the slip the subclass number in which the cross-reference shall be mounted. If the matter to be cross-referenced relates only to a portion of a voluminous patent, the portion of the specification and drawing to be cross-referenced should be indicated. If the cross-reference falls outside the class, the class number should be noted in addition to the subclass number.
(12) Should it be found that the handling of copies in making examinations detaches the cross-reference slips, it may be advisable to mark lightly but legibly in pencil on the lower right-hand corner of the examiner's photolithograph the number of the subclass or subclasses into which it is to be cross-referenced, or the number of the class and subclass in case it is to be cross-referenced to another class.
(13) Whether cross-reference notations are written on a separate slip or on the photolithograph, the number of the class and subclass into which a patent is to be cross-referenced should always be preceded by X (thus X 101-23) in order to distinguish the original classification notation from the cross-reference notation and enable sorting and indexing to be done without confusion.
(14) To indicate cross-references from other classes into the one being reclassified, set down the number of the patent in a notebook, placing after the number (1) the class and subclass in which it is classified; and (2) the number of the class and subclass in which it is to be cross-referenced.
(15) Should new subclasses be formed or transfers of patents be determined on, and lists of the patents, instead of copies thereof, be furnished clerks for the purpose of making such subclasses and transfers and correcting the official indexes and other records, each patent should be listed by number in column to the left of a sheet of paper or notebook, and opposite each patent number on the same sheet should be written (1) the number of the class and subclass in which it is officially classified; (2) the number of the class and subclass to which it is intended to transfer it; and (3) the numbers of the classes and subclasses, preceded by X, into which it is intended to cross-reference it.