(1) Subject to the provisions of paragraph (2)(ii), drawings shall be required when they are necessary for the understanding of the invention.
(2) Where, without being necessary for the understanding of the invention, the nature of the invention admits of illustration by drawings:

(i) the applicant may include such drawings in the international application when filed.
(ii) any designated Office may require that the applicant file such drawings with it within the prescribed time limit.

Flow sheets and diagrams are considered drawings.

The time limit referred to in Article 7(2)(ii) shall be reasonable under the circumstances of the case and shall, in no case, be shorter than two months from the date of the written invitation requiring the filing of drawings or additional drawings under the said provision.

The size of the sheets shall be A4 (29.7 cm x 21 cm). However, any receiving Office may accept international applications on sheets of other sizes provided that the record copy, as transmitted to the International Bureau, and, if the competent International Searching Authority so desires, the search copy, shall be of A4 size.

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(c) On sheets containing drawings, the surface usable shall not exceed 26.2 cm x 17.0 cm. The sheets shall not contain frames around the usable or used surface. The minimum margins shall be as follows:
- top: 2.5 cm
- left side: 2.5 cm
- right side: 1.5 cm
- bottom: 1.0 cm

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(a) The drawings shall not contain text matter, except a single word or words, when absolutely indispensable, such as “water,” “steam,” “open,” “closed,” “section on AB,” and, in the case of electric circuits and block schematic or flow sheet diagrams, a few short catchwords indispensable for understanding.

(b) Any words used shall be so placed that, if translated, they may be pasted over without interfering with any lines of the drawings.

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(a) Drawings shall be executed in durable, black, sufficiently dense and dark, uniformly thick and well-defined, lines and strokes without colorings.
(b) Cross-sections shall be indicated by oblique hatching which should not impede the clear reading of the reference signs and leading lines.
(c) The scale of the drawings and the distinctness of their graphical execution shall be such that a photographic reproduction with a linear reduction in size to two-thirds would enable all details to be distinguished without difficulty.
(d) When, in exceptional cases, the scale is given on a drawing, it shall be represented graphically.
(e) All numbers, letters and reference lines, appearing on the drawings, shall be simple and clear. Brackets, circles or inverted commas shall not be used in association with numbers and letters.
(f) All lines in the drawings shall, ordinarily, be drawn with the aid of drafting instruments.
(g) Each element of each figure shall be in proper proportion to each of the other elements in the figure, except where the use of a different proportion is indispensable for the clarity of the figure.
(h) The height of the numbers and letters shall not be less than 0.32 cm. For the lettering of drawings, the Latin and, where customary, the Greek alphabets shall be used.
(i) The same sheet of drawings may contain several figures. Where figures on two or more sheets form in effect a single complete figure, the figures on the several sheets shall be so arranged that the complete figure can be assembled without concealing any part of any of the figures appearing on the various sheets.
(j) The different figures shall be arranged on a sheet or sheets without wasting space, preferably in an upright position, clearly separated from one another. Where the figures are not arranged in an upright position, they shall be presented sideways with the top of the figures at the left side of the sheet.
(k) The different figures shall be numbered in Arabic numerals consecutively and independently of the numbering of the sheets.
(l) Reference signs not mentioned in the description shall not appear in the drawings, and vice versa.
(m) The same features, when denoted by reference signs, shall, throughout the international application, be denoted by the same signs.
(n) If the drawings contain a large number of reference signs, it is strongly recommended to attach a separate sheet listing all reference signs and the features denoted by them.

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(a) Drawings are required when they are necessary for the understanding of the invention (PCT Art. 7).
(b) The physical requirements for drawings are set forth in PCT Rule 11 and shall be adhered to.