Checkmate is a testing-only utility. Many problems tested by Checkmate reflect hardware failures, and 'repair' actually requires taking your Mac in for service. In some cases, volume structures errors can be 'fixed' by the action of unmounting the drive and testing it. This can result in a 'passed' result being reported by other utilities after Checkmate reports a failure. Techtool Pro can also be used to repair some types of failures.