I know many of you use air tools and to drive them have an air compressor.  I have one of the 60 gallon upright models and the one thing I always hated about it was bleeding it after I was done using it.  The petcock liked to stick and being that you are bending down and the valve is up-side-down I could never remember which way to turn it.  Any way because it was a pain to use I didn't bleed it every time... in fact I went way longer than I should have to bleed it.  I decided I was way over due and went to bleed it yesterday and found the petcock completely frozen.  So I let all the air out of the tank and removed the petcock.  I took it to the hardware store but they didn't have one in the correct size.  What they did have was this.

I don't know why I didn't think to switch out to a ball valve a long time ago.  This should be  a much better option, easy to use, less likely to freeze up, and a slick way to go.  Just thought I would pass it on.