37 CFR 1.74: Reference to drawings
Taken from the Ninth Edition of the MPEP, Revision 10.2019, Last Revised in June 2020
1.74 Reference to drawings.
When there are drawings, there shall be a brief description of the several views of the drawings and the detailed description of the invention shall refer to the different views by specifying the numbers of the figures and to the different parts by use of reference letters or numerals (preferably the latter).