Use rule of thumb in a sentence?

'Rule of Thumb' was a very wise English rule that stated a man was not allowed to beat his wife with a stick thicker than his thumb. Since that time, 'thumb rule' has come to describe various rough general guages for various activities and actions; waiting half-an-hour after eating before swimming, even though ther is no medical reason to do so, has become a 'thumb rule' for mothers. A case could be made for the 'Third Date Rule' being a rule of thumb. In Finance, the 'Rule of 72', i.e. that a given interest rate will double when the rate and the years multiplied equal 72; 6% interest for 12 years will double your money, 2% times 36 years, etc., would be a rule of thumb.