On the web and in print, you find frequent mention of a “lean toolbox,” “lean toolbook,” or similar. These books do have their use, and at least one of them is written by an author that I highly respect. Many other lean books also focus on the different tools and methods. But focusing on a set of tools can also be quite misleading. Hence, I wrote this blog post as a word of warning. Every master needs their tools, but the tools do not make a master!