How does one register a "shutdown hook"!

[Chris Ross <cross%distal.com@localhost>]

  When I shutdown my netbsd-5 (RC3), I see:

About to run shutdown hooks...
Stopping cron.
Stopping inetd.
Waiting for PIDS: 495.
Stopping squid[........].
Removing block-type swap devices
swapctl: removing /dev/sd0b as swap device
Mon Aug  2 22:45:10 EDT 2010

Done running shutdown hooks.

  So, since I'm running pkgsrc conserver8 on this machine, and "cleanly" 
shutting down the connections to the console server would theoretically be a 
good idea, what do I need to do to the rc.d action, or anywhere else, to 
declare that "stop" action as a "shutdown hook"?

  Thanks...

              - Chris