do you know what 'the rule of thumb' is?

yes. it comes from england a long time ago when men could beat their wives for acting out. the law that was in place stated that a man could onyl beat his wife with a stick no wider than his thumb...hence the saying "rule of thumb"

The real explanation of 'rule-of-thumb' is that is derives from wood workers (or other constructors) who knew their trade so well they rarely or never fell back on the use of such things as rulers. Instead they'd measure things by, for example, the length of their thumb; they measured, not by a ruler of wood, but by rule of thumb.

It now means a practical estimation or standard.

I believe the "wife beating" origin is a very popular myth.

That cliche tends to be used as "the unspoken rule" or just "the rule"

I cant put my finger on what the thumb is about ;) It's on the tip of my tongue... lol

the rule of thumb could be the right hand and left hand thumb rule by fleming associated with electricity and magnatism...it is the principal behind the working of electric motor and generator

that a man can beat his wife with a poll no thicker than his thumb

The first answer you had is 100% correct.

Check this sight out, it gives a good explanation

http://en.wikipedia.org/wiki/Rule_of_thumb