In the context of German patent law, the Formstein defence is a well-known defense against an alleged infringement by equivalents, wherein the alleged infringer claims that the embodiment alleged to be equivalent (to the subject-matter claimed in the patent) is not patentable and therefore the doctrine of equivalents does not apply.
[1] It is similar to the UK's Gillette defense and the U.S. Wilson case.
[2][3] The name "Formstein" means "molded kerbstone" and comes from a landmark decision of the Federal Court of Justice of Germany (Bundesgerichtshof) issued in 1986.
[2][4][5] This article about German law is a stub.
You can help Wikipedia by expanding it.