"A rule of thumb is a homemade recipe for making a guess," writes Tom Parker in his book of compilations, "Rules of Thumb 2."
"It is an easy-to-remember guide that falls somewhere between a mathematical formula and a shot in the dark.
"A rule of thumb is not a tool. Pull a good one out of your hat and--abracadabra--you turn information you have into information you need.
"Frankly," Parker writes, "I can't say that all of these rules of thumb work. Some would be pretty hard to test. Consider these a treasury of private inventions that work for the people who sent them in."
Here are some examples that are more appropriate to summertime activities:
--Elsbeth Cates, writer, Rising Star, N.D., in New Age Journal
--Ned Frederick, writer, Exeter, N.H.
--M.J.T. Ferguson, retired taxi driver, Narberth, Penn.
--Bruce Reznick, associate professor of mathematics, Urbana, Ill.