Security tagging schemes are known as promising mechanisms for providing security features in computer systems. Tags carry information about the tagged data throughout the system to be used in access control and other security mechanisms. This paper discusses several different uses of security tags related to different security policies, highlighting appropriate uses of the tags. The evaluation of the use of tags is presented in the summary of three security tagging application domains. One domain, using hardware-based tagging to prevent high-level attacks, was not found to be feasible. A project to use hardware-based tagging for OS security enhancement and a project that uses software-based tagging for multi-level secure document management were successful.