The Patent Cooperation Treaty (PCT) provides regulations for drawings in international patent applications. Here are some key regulations related to PCT drawings:

1. Format: Drawings should be presented in a clean, clear, and permanent form. They should be executed in durable, black, sufficiently dense and dark, uniform, and well-defined lines.
2. Numbering: Drawings should be numbered in Arabic numerals consecutively and must be identified with the same application number and international filing date as the rest of the application.
3. Size: The sheets should be of A4 size, measuring 210 x 297 mm.
4. Margins: Drawings should have margins of at least 15 mm at the top, left and right-hand edges and 35 mm at the bottom.
5. Views: Drawings should be represented in a way that fully and clearly discloses the invention. Different views such as plan, elevation, section, or perspective should be used where necessary to provide a complete understanding of the invention.
6. Labeling: Each drawing should be labeled with the title of the invention, the name of the applicant, and the figure number.
7. Corrections: Corrections or amendments to the drawings must be made in such a way that the clarity and legibility of the original drawing are not impaired.
8. References: If reference is made to a prior application or patent, the drawing should include a reference to the number of the prior application or patent and the drawing or figure number in the prior application or patent.

These regulations ensure that PCT drawings are presented in a uniform and standardized manner, allowing examiners to easily understand the invention and evaluate its patentability.