I picked up a book at the Lifeline Bookfest that I thought would interest my husband, but then found that it's useful for me too. It's called "Tools and their uses" and it was originally prepared by the Bureau of Naval Personnel as a handbook for US navy. The manual is so useful that it was subsequently printed for use by anyone interested in "learning the basics of choosing tools and using them as they were meant to be used".
The first paragraph of the back cover says "Do you have trouble with tools - find they wear out too quickly, find that you can't decide which tools to buy or which tools to use for a specific job, find that things continually go wrong? The only way to learn to use tools, of course, is by using them, but first you have to know which tools to use and why."
The manual is full of a wealth of diagrams and simple explanations and I finally found out about how to use washers properly. Flat washers are used with nuts to provide a larger connecting area to prevent the nut head from damaging the work surface. Split lock washers are used under nuts to prevent loosening by vibration. The ends of these spring-hardened washers dig into both the nut and the work to prevent slippage. Shakeproof lock washers have teeth or lugs that grip both the work and the nut.
So now you know.
This is the lower half of a page that's made to look like it's notes pinned to a corkboard. The upper part is the pic in the "About Fat" entry. I like the effect.