This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
Screw-top fruit jars may be easily opened in the following manner: Secure a strap with a buckle and place it around the top as if it were to be buckled, but instead draw the loose end back and hold it with the thumb as shown. Turn cover and strap while held in this position and it will easily turn from the jar. - Contributed by Chas. A. Bickert, Clinton, Iowa.