[see the tklib CVS repository if you don't see this module in your version]
Here is a quote from the manpage (as found in the CVS respository):
[add info on what this is, how it works, screen image of what it looks like, whatever]
Focus seems to be on managing and keeping consistent the items in the diagrams, rather than (the higher level problem of) layout.
Drawing Diagrams may be related to this package