...It describes what it is going to do (including showing the exact commands that will be run), then calls twadmin, mktwpol.sh and tripwire to make key files, generate tripwire policy, encrypt the policy, and make the tripwire database.
mktwpol.sh is a bash script that creates a plain-text tripwire policy file tailored to the packages and files currently installed on a system. The mktwpol-generic.sh script (not included in the release tarballs, but can be found in the "code" section) can be adapted to Linux distributions other than Gentoo.