Delivering a high-quality body of work that is hard to replicate is the second true mark of an expert. Sometimes your expertise is the consequence of your knowledge, but often it is the result of unmatched execution. You are an expert because you can do things that other people cannot do, or you can perform at a level of proficiency that other people cannot match.

The doing often distinguishes the expert much more than the knowing. There are, of course, some professions where knowledge is the primary measurement of expertise, such as for college professors and politicians. All experts must have knowledge, but for most experts, knowledge is not enough. It is the quality of execution that is paramount.

An orthopedic surgeon I once interviewed was happy when his practice finally hired a new surgeon. After months of searching, the medical group found a qualified young doctor who they thought could perform the procedures required at the large, busy medical practice. Shortly after the new surgeon started, however, it became clear that he did not measure up ability wise to the expectations of the other surgeons or patients. Eventually, the new surgeon was let go and the group started another lengthy search.

Great experts don’t just have knowledge about their field; they also have the ability to deliver a high-quality body of work independent of assistance. This applies to surgeons, engineers, and any other SME. Great experts look for ways to translate their expert knowledge into expert performance. They look for ways to distinguish themselves through the things they do, rather than the things they say.