How to pack cron jobs?

["Pavel Alexeev (aka Pahan-Hubbitus)" <forum ru bir ru>]

Hello.

I'm search documentation, how-to or guidelines how I can correctly pack 
cron job, needed by rpm package.

I'm spent big time, but do not find any useful description.

Off course I known about directories
/etc/cron.daily
/etc/cron.hourly
/etc/cron.monthly
/etc/cron.weekly
but what if I need start job every 20 minutes?

AFAIK, in cronie rpm presents /etc/cron.d especially for this purposes. 
But really it is only true way put cronie into requires? How I can pack 
jobs for standard (vixie) cron?

Very thanks for all answers.