The drawings must 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. Any words used must be so placed that, if translated, they may be pasted over without interfering with any lines of the drawings.
Any text matter which is indispensable must comply with the requirements for the writing of text matter.
For indications of the type "section on AB", see GL/PCT-EPO A‑V, 7.3.1.
Where any text matter of the drawings is filed in a language which is different from the language of the description and the claims, the receiving Office will invite the applicant to furnish a translation of the text matter of the drawings into the language in which the international application is to be published (Rule 26.3ter). The receiving Office decides whether the correction was submitted within the two-month time limit under Rule 26.2 and, if so, whether the international application so corrected is or is not to be considered withdrawn. However, no international application may be considered withdrawn for lack of compliance with the physical requirements referred to in Rule 11 if it complies with them to the extent necessary for the purpose of reasonably uniform international publication (Rule 26.5).
GL/RO 55, 57, 62 and 63