"The drawings should be made and lettered, so that the specifications can be written up, including the proper reference to the different parts.
"The drawings should be made upon paper stiff enough to stand in a portfolio, the surface of which must be calendered and smooth. The best kind is patent office bristol, though there is a style on the market printed with margin and headings all ready for use, but the surface is not of the best.
"The size of the sheet on which a drawing is made should be exactly 10 × 15 inches with margin lines one inch from all the edges, leaving a clear space of 8 × 13 inches.
"One of the smaller sides is regarded as its top, and measuring downward from the margin, or border line, a space of not less than 11⁄4 inches is to be left blank for the insertion of title, name, number and date, to be put in by the patent officials.
"All drawings must be made with the pen only, using the blackest India ink. Every line and letter, including the signature must be absolutely black.
This applies to all lines, however fine, to shading and to lines representing cut surfaces in sectional views. All lines must be clean, sharp, and solid, and they must not be too fine or crowded.
"Surface shading, when used, should be left very open. Sectional shading should be by oblique parallel lines, which may be about one-twentieth of an inch apart. Drawings should be made with the fewest lines possible consistent with clearness, for the drawings are subjected to photographic reduction, which decreases the space between the lines.
"Shading (except on special views) should be used only on convex and concave surfaces, and there sparingly, or it may be dispensed with if the drawing is otherwise well made.
"The plane on which a sectional view is taken should be indicated on the general view by a broken or dotted line.
"Heavy lines on the shade sides of objects should be used, except where they tend to thicken the work and obscure the reference letters.