Written Description
The written description must convey that the applicant has reduced the claimed subject matter to practice. At this point, the invention has been physically created it, is fully operational and complete, and its full utility is known. No other experimentation should be necessary in order to make the invention work. Reduction to practice may be done by another on behalf of the inventor.

For example, the following types of inventions are considered reduced to practice after the subsequent condition is fulfilled:

• process - when it is successfully performed
  
• machine - when it is assembled, adjusted and used
  
• manufacture - when it is completely manufactured
  
• composition of matter - when it is completely composed

There must be sufficient testing to demonstrate that the invention will work for its intended purpose, however, it does not have to be in a commercially satisfactory stage.

Applicants must prove they know how the invention works; from how to build it to how to use it. The invention must be completely worked out, with nothing left to the imagination. The written description should allow people of ordinary skill in the art to recognize that the inventor was "in possession" of the claimed invention and knows how to make and use it. To summarize, the written description is a section within the application where the applicant convinces the reader that he or she was in possession of the claimed subject matter.

Enabling disclosure
The specification must also include an enabling disclosure. Translated, this means that the specification must actually show how to make and use the invention. This enablement must be described so that people of ordinary skill in the art can make and use the invention without having to experiment.

Let's use Silvia for an example. Silvia comes up with a fabulous new way to purify and sequence DNA, but other molecular biologists cannot just sit right down and use her method after reading her specification. This is because she did not provide a good enabling disclosure. Informative pieces are missing. Without these pieces of information, no one could make her methods work without experimenting. Therefore, the PTO will reject her application under 35 U.S.C. 112, 1st paragraph. The lesson is, make certain the invention really works and describe it well enough so others can make and use it without any trouble.


Best Mode
We should give the PTO credit for making the best mode a requirement. Basically, an inventor (or joint inventor) must put the "best mode" of making and using the invented subject matter into his or her application. Take the DNA example from the previous section. Using her process for purifying and sequencing DNA, Silvia purifies and sequences thousands of DNA strands in minutes. Her technology is the best in all of the land. In fact, it is so good that Silvia doesn't want to share it with the rest of the world. She wants her lab to be the most productive lab around. So Silvia holds back a thing or two from her specification. She conceals the best parts of her new method. But, in doing so, the best mode requirement will not have been satisfied and as discussed, that is grounds for a rejection under 35 U.S.C. 112, 1st paragraph.