Regulation 21

top: 2.5 cm;

left side: 2.5 cm;

right side: 1.5 cm; and

bottom: 1.0 cm.

without colouring in durable, black, sufficiently dense and dark, uniformly thick and well-defined lines and strokes to permit satisfactory reproduction;

cross-sections shall be indicated by oblique hatching which should not impede the clear reading of the reference signs and leading lines;

the scale of the drawings and the distinctiveness 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. If, as an exception, the scale is given on a drawing, it shall be represented graphically;

all numbers, letters and reference lines, appearing on the drawings, shall be simple and clear and brackets, circles and inverted commas shall not be used in association with numbers and letters;

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;

the height of the numbers and letters shall not be less than 0.32 cm and for the lettering of drawings, the Latin and, where customary, the Greek alphabets shall be used;

the same sheet of drawings may contain several figures; where figures drawn on 2 or more sheets are intended to form one whole figure, the figures on the several sheets shall be so arranged that the whole figure can be assembled without concealing any part of the partial figures; and the different figures shall be arranged without wasting space, clearly separated from one another and shall be numbered consecutively in Arabic numerals, independently of the numbering of the sheets;

reference signs not mentioned in the description or claims shall not appear in the drawings, and vice versa; and the same features, when denoted by reference signs, shall throughout the application, be denoted by the same signs;

the drawings shall not contain textual matter, except, when required for the understanding of the drawings, a single word or words such as “water”, “steam”, “open”, “closed”, “section on AA”, and in the case of electric circuits and block schematic or flow sheet diagrams, a few short catchwords; and

the sheets of drawings shall be numbered in accordance with rule 23(13) and (14).