Mark a test case as Final

A test case can have a status of either Draft or Final.  You can mark a status as Final in the test case details window. Click the Draft status to expand a dropdown, then select Final. Once it is marked as Final, it can not be moved back to Draft. A new version may be derived from this Final version if you would like to make changes. 

Users will need view and edit permissions for test coverage to change the test case status.