RE: Do NOT risk your life NEEDLESSLY...
Thanks, Bob.
This simple step doesn't cost that much, can be used year after year and best of all it works.
Statjunk, the prusic knot can fail, which is why I spent the $40 for the ascender (and no one pinches a penny more than I do!). Because the prusic can fail, most rock climbers will not use them in any serious situation.
Here's how I look at it: I spent a pile of money on gear and clothes (I won't bore you with a list that we're all to familiar with). Why would I not spend an extra $100 bucks or so to PREVENT myself from being seriously injured or killed.
If you use the prusic, test it regularly near the ground. I was in the US Navy for many years so I'm familiar with the knot but I don't like it because it is much more difficult to slide up as you climb when compared to the ascender.