You might be thinking, "If this tutorial is any good, I should be learning stuff on Page One".

This is for you:

a "mil" is one-thousandth of an inch
 

Circuit board designers who aren't using the metric system tend to "speak in mils".

At my first meeting at my first job as a circuit board designer, I asked, "What's a mil?"

and everyone looked at me . . . .

. . . . as if hiring me was the biggest mistake the company had ever made.

So the next time someone says,

"An 8 mil trace on one-ounce should handle 1.2 amps at 20 degrees over ambient, but beef it up a little to cut the inductance."

at least you'll know what the "mil" part means!

(thanks to Laser Precision for giving me my first job)