Maybe they are talking about squaring the dies setting up. check out this link. Tells alot about it. Very imporant for seating die setup. But using a plain ole washer isn't good. It has to be uniform by .0005" I think to be of any use. A home depot washer ain't that. I had my machinist here at work just mill me a nickel size piece of steel.

http://www.sierrabullets.com/xring/i...l1no1#loadtip1

And
http://www.sierrabullets.com/xring/i...ol1no2#loadtip