Beginning with later versions of System 7, "tomes" have existed to hold, and compress, Installer content. The Installer takes advantage of tomes by extracting items from the tomes and placing them in the correct location on the Macintosh.
TomeViewer allows the user to pry open any tome and to extract one or multiple items from therein. While it is useful for the extraction of a certain number of files, the use of TomeViewer to extract and install in place of the actual application of the Installer is not recommended, as the Installer may, from time to time, perform operations that modifies system items (e.g. the System file). Extracting and placing individual installer components do not actually modify the System file on their own.
TomeViewer is useless on Mac OS X except for in the Classic environment. For Mac OS X users, a utility called Pacifist does the same thing to Mac OS X packages. It can be downloaded at VersionTracker.
Instructions on how to use TomeViewer can be found at http://home.arcor.de/grouchosbox/tomeviewer.html .