"Old Saying Shows Guess Estimating That's Close" by Susan Pearl

"As a rule of thumb".


My thumb measures 3/4 of an inch across the middle of  the thumbnail  If something needed to be 1 and 1/2 inches long or wide I could estimate that distance by using my thumb width twice( because 3/4 inch plus 3/4 inch equals 1 and 1/2 inch).  It made not be as accurate and a ruler but it is a "rule of thumb".

The old saying "as a rule of thumb" is also used to guess an estimation of something by previous known experience of a similar setting.  Like, "as a rule of thumb" when a store owner takes inventory he (she) can see when it is time to reorder.  The "rule of thumb" is used as indictors to show approximate timing or spacing.  Actual testing and ruler measurement are more reliable but it is nice to, also, have a rule of thumb to go by in general.