Four corner method

From Carls wiki

"For looking up unfamiliar characters there is another method called the four-corner system. This method is very fast — rumored to be, in principle, about as fast as alphabetic look-up (though I haven't met anyone yet who can hit the winning number each time on the first try). Unfortunately, learning this method takes about as much time and practice as learning the Dewey decimal system. Plus you are then at the mercy of the few dictionaries that are arranged according to the numbering scheme of the four-corner system. Those who have mastered this system usually swear by it. The rest of us just swear."
— David Moser, Why Chinese Is So Damn Hard

Links

• Four Corner System for Searching Character Indexes and Computer Input
• An overview of the four corner coding system