Patent Application Drafting: Ambiguity and Assumptions are the Enemy

caution-warningShould inventors be going solo, filing a patent application and trying to protect their own inventions? No, at least not if you can afford to hire a patent attorney. Going solo through this patent maze would be similar to trying to remove your own appendix. If you can get to a hospital you should not be removing your own appendix! It is that simple. But there will always be inventors who will proceed on their own. Sometimes this is due to hubris, but frequently it is out of necessity.

There is nothing wrong with representing yourself if the choice is between DIY or not moving forward, but for those who will go it alone it is imperative that they become as familiar as possible with the rules, regulations and best practices. It is for these do-it-yourselfers who proceed out of necessity, but with their eyes open, that I write this and other similar articles.

One very common mistake inventors will make is that they will want to only describe their invention in the most general terms possible. Why would you want to be specific, they ask, because if you are too specific it will be easy for people to get around your patent. It is true that an unnecessarily specific discussion of the invention in a patent application can make it easy for competitors to copy your invention without infringing your patent, but if you file an application that only generally, or vaguely, describes the invention that is even worse.

There is a fine line between being too specific and being too general, and that fine line is mostly to do with how you say things. In my experience the near universal problem inventors have is that they are far to general and vague. Only in the most rare case do you see an inventor who compromises their rights by being too specific. And the problem with being too specific is not associated with providing too much detail, but rather how you express the detail. If you only ever describe your “invention” or the “present invention” as being made up of A, B, C and D, then you cannot say that your invention is A, B and C. For this reason having multiple examples of various versions of your invention is critically important. Being too specific is another topic for another day. Today’s lesson is about avoiding ambiguity and making assumptions.


Ambiguity is the real problem do-it-yourself inventors face. This is understandable to some extent because if you have a real innovation you as the inventor will know it best. Much of what you have done will be clear to you, so many just assume it will be clear to the reader as well. Whenever you are drafting a patent application it is dangerous to assume that the reader will fill in any ambiguous holes you leave in the manner you desire.  Thus, it is critical for the drafter to be as explicit and precise as possible.

Along these same lines, inventors need to be cautious about assuming any particular knowledge or understanding on the part of the reader. It is true that you are able to describe your invention such that someone of reasonable skill in the field would understand it, but determining who is one of reasonable skill and what level of understanding they possess requires making a legal determination that most inventors are not qualified to make. Thus, the do-it-yourself inventor better off assuming an intelligent audience, but not assuming any particular expertise.  This should make you choose your words carefully in order to convey the most precise meaning, which is what you should strive for in a patent application. It will also make you explain the invention without leaving any holes or making any assumptions. This will lead to more explicit disclosure, which will necessarily lead to implicit and inherent disclosure.

I often tell inventors (and law students) that they should try and describe an invention in words that would convey meaning to someone who is blind. This is a tough task no doubt, but the goal of the written disclosure is to provide a description that is much like a step by step how-to manual. If you are trying to describe your invention to someone who cannot see then you will invariably find creative and enlightening ways to  get your message across. This is the type of detail that should be in a patent application.

In several articles I have gone into detail about how to effectively use drawings to help convey a better, more detailed and simultaneously broad understanding of the invention. See Working with Patent Drawings to Create a Complete Disclosure and Patent Drawings 101: The Way to Better Patent Applications. I won’t belabor the point here, but by suggesting that you describe your invention so that someone who is blind can understand what you are disclosing I am in no way suggesting that drawings are unimportant. Good patent drawings must be thought of as essential! The single best, cheapest way to expand any disclosure is to have good patent drawings. I think patent applications as a general rule have far too few patent illustrations. The more the merrier, and the more you have the more that will be disclosed. By having numerous drawings you also force yourself to describe what is shown in each drawing. If you combine this with the previous advice about describing the invention so someone who is blind can follow along you should wind up with an excellent disclosure. But always look for ways to add additional drawings, whether they are views from different vantage points, exploded views, or drawings that show individual pieces and parts, professional patent drawings provide a crucial safety net because anything shown in the drawing is considered disclosed.

Another way to help explain the level of detail necessary for a patent application is to think about how children describe things, perhaps when doing a “show and tell” at school. Kids will explain EVERYTHING, no matter how obvious. They over describe because they have no idea what the person listening knows, and to them it is all new and interesting, thus they explain everything with tremendous detail (whether you want to hear it or not). That is exactly what you need to do in a patent application. Explain your invention with so much detail that you will bore the knowledgeable reader to death. While this should be easy for inventors it is frequently difficult because so many times friends and family have shown disinterest for so long. Try and capture that inner excitement you have and describe your invention as you would to someone who is genuinely interested, perhaps envision telling every detail about your invention to someone you really want to impress. This is the level of detail you need!

Always remember that as you are explaining your invention the design purpose may be helpful to tell the story of your invention from a historical perspective, but a patent application is not intended to be a historical document. A patent application needs to describe the structure.

Along these same lines, explaining the function of the invention is helpful, but only explaining something in terms of function leaves many questions unanswered because it is not terribly descriptive. For example, assume you are unfamiliar with a couch. If I were to try and describe a couch by explaining that you sit on it to watch TV, would that bring to mind a couch? It might, but it might also bring to mind a chair (of various sorts), a recliner or perhaps a love seat. Maybe even a bar stool. Notice also that when describing the couch for sitting we are leaving out lying on the couch. If I were to describe the couch structurally, however, the reader would be able to understand that you could sit on it or lay on it. The description would also easily distinguish the couch from a bar stool or chair. Thus, describing function can be helpful to get the reader thinking in the right direction, but normally it does not bring the reader all the way to an unambiguous understanding.

The moral of the story is this: When drafting a patent it is essential that you remove any ambiguity.

For more on drafting a patent application please see:


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