Fence Posts or Sign Posts: Rethinking Patent Claim Construction


  • Mark Lemley
Publish Date:
June 1, 2009
Publication Title:
157 University of Pennsylvania Law Review 1743 .
Journal Article
  • Dan L. Burk & Mark A. Lemley, Fence Posts or Sign Posts: Rethinking Patent Claim Construction, 157 University of Pennsylvania Law Review 1743 (2009).


Patent law is bogged down in the minutia of claims construction. Claim construction is central to every patent dispute, but it has not provided the hoped-for certainty or notice to competitors. Quite the contrary: disputes about the importance of inventions and the scope of patents have been replaced by labyrinthine wrangling over words written by lawyers. The flaws of claim construction result largely from the problems attending “peripheral claims,” that is, claims that purport to set the outermost boundaries of patent rights. In this paper, we argue that the way for the patent system to move ahead may be by looking behind, to the practice of “central claiming” that was prevalent before 1870, and which was used in many countries through the late twentieth century. Rather than relying on the illusion of peripheral “fence posts,” patent law may do better to once again look to stability of central “sign posts.” We examine the failure of peripheral claiming, the benefits of central claiming, and several hybrid measures that might be adopted, either in the process of moving from fence-posting to sign-posting, or as improvements over the current system that still stop short of fully adopting central claiming.