How to remove a binary package?

I may have a need to install one or more binary packages to fix
a problem I'm having.  These are ones that have been made for
my system during normal emerges, but have since been pruned from
the system.

My question: how to clean up when I'm done?  A cursory look at
the packages makes me think they're plain tar archives with no
metadata.  How do I get rid of them when I'm done with them?

Or must I install them using some tool that creates the metadata?

++ kevin

-- 
Kevin O'Gorman, PhD