Look at these!  Such a plethora of various door opening devices, and these are just a sampling.  Door knobs have been around since the 1800's and have become an object so common, they are often taken for granted...that is until it breaks when you're inside the bathroom.  Then, a rush of appreciation for every door knob you have ever known that has worked at your command comes over you.  You gain a sentimental attachment for those silent sentinels who solemnly sit upon the doors of your life.  ...just kidding. Usually you just get mad that it's not working.  Want to know what makes them work? 

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