Don’t use it.
The specification and patent claims are two important components of a patent application. Do not use reference signs in the invention content part of the description. Reference signs may (or more often do not) appear in the claims, but remember to enclose the figures in parentheses.
A patent specification is a clear and complete introduction to the structure, technical points, and usage of an invention or utility model. It should include the technical field, background technology, invention content, description of the drawings, specific implementation methods, etc. project.