How to Stake the Castle nut?

I have a couple of Magpul’s on my AR’s. They are not staked, what tool do I need to stake them? Are there more than one method?

Tips, tricks advise? It keeps bugging me that they are not staked.

http://m4carbine.net/showthread.php?t=6994

Thank you. Just went to Harbor Freight and bought a one. It worked pretty good. Thanks . Did four of them, used some Blueing and cleaned it up a bit.