[gentoo-user] `sets' & sets.conf

[Harry Putnam]

Can anyone post, in laymans, terms how to use sets.conf.  Or thru
FEATURES if thats how its done, I've read the posrtage manpage that
covers it and this URL:

https://dev.gentoo.org/~zmedico/portage/doc/ch02s02.html#config-set-syntax-single

Finally reinstalled portage with USE="doc" to get the html set
referred to in portage manual as the definitive place to learn about sets

But honestly I left those without a stinking clue how to actually use sets
for things like avoiding specific packages being depcleaned.  I mean
besides putting them in `world'

There seems to be a durth of what actually to put into make.conf under
FEATURES or whatever...

I want to protect certain pkgs from depclean.... how can I put a small
list under `sets' management in make.conf or sets.conf or ....