Most inventions will require a drawing or two along with the specification in order to help understand the invention. However, drawings are not a necessity in each and every patent application. But if an application is missing a necessary drawing, it will be considered incomplete. However, applications which are not design applications that are filed on or after December 18, 2013 are entitled to a filing date even if the application does not contain drawings. If such an application is filed without drawings, the drawings may be sent in subsequent to its filing date.

Drawings are usually in black and white ink. However, color drawings may be necessary in rare instances, and will be accepted if they are accompanied by the required fees.

Photographs are not usually allowed, but they may be accepted if a photograph is the only practical way to illustrate the claimed invention. In these cases the required fee must be included along with a petition.  Many biotechnology related applications contain photographs since drawings cannot accurately replicate the results of most experiments. In addition, some design applications require photographs instead of drawings due to the nature of the invention.

There are quite a number of rules associated with drawings. For example, drawings must show every feature of the invention. In addition, graphic drawing symbols and other labeled symbols may be used wherever they are appropriate. Lastly, the views in a drawing must never be connected by projection lines or contain center lines.

Models are usually not admitted into a patent application. However, there are times when specimens are required, especially for biotechnology related inventions. In instances like these, the inventor will have to supply seeds or actual cells to the PTO as a deposit along with the completion of a petition.