Picked up some scrap steel from work today.  It's about a 1/4" thick.  Any ideas has to how to tell if it good for knives?

Toss it in your BBQ, and let it get red hot, then quench it in water, put it in a vice, and smack it with a hammer.

If it bends, its not suitable for a knife. If it breaks, its hardenable.

A spark test will give you some idea of the carbon content.

http://www.aussieweld.com/arcwelding/page15/chart2.gif

I'm with Wampus hillbilly.  

I use the spark test all the time.  Just remember that you need to use a high speed grinder...10,000 rpm or higher to do the test.  But most right angle grinders are anyway, so that shouldn't be a problem.

And do it in a low light area. Makes it easier to see.

Thanks for the info guys I appreciate it.  Hopefully it amounts to something and not junk steel.