Arabic numerals, Latin letters and Roman numerals written on engineering drawings can be written in italics or straight. When Latin letters are used as symbols alone, I, O and Z are not used to avoid confusion with Arabic numerals 1, 0,2. The writing and arrangement of Latin letters, Arabic numerals and Roman numerals shall comply with the provisions in Table 4.0.5. ? If Latin letters, Arabic numerals and Roman numerals need to be written in italics, they should be inclined 75 counterclockwise from the bottom line of the characters.

The height and width of italics should be equal to the corresponding straight characters. ? The word height of Latin letters, Arabic numerals and Roman numerals should not be less than 2.5 mm. The numerical annotation of quantity shall be written in Arabic numerals. Various units of measurement with numerical values in front should be marked with unit symbols promulgated by the state. Unit symbols should use orthographic letters. Fractions, percentages and proportions shall be written in Arabic numerals and mathematical symbols. For example, 3/4, 25% and 1: 20 are written as 1:20 respectively.