Where else can one turn for miscellaneous information when google is just not sufficing? TALKBASS OF COURSE! Well, this question goes out to all you Sudoku buffs! (There has to be some right? - I mean, we are an intellectual breed!) I have been doing "evil" difficulty puzzles from websudoku.com. I can typically get through these using a few basic and some advanced strategies. However, I have been working on this one puzzle for quite a few days at work and cannot seem to get beyond my current position. I decided to try out the strategy called the "X-Wing" It seems pretty simple... 2 columns and 2 rows with the same number in each and form a square/rectangle. From what I understood, when you have this pattern established, than those numbers should be the proper numbers to be used. However, in the same puzzle, in the same exact spots, I have two different sets of numbers (1,9) that form the X-Wing pattern, but NEITHER of them actually worked out properly and led to mistakes. Is there something I am missing on the X Wing strat? Does the X Wing ALWAYS work - I know I cannot always pick the right number, but I can usually eliminate other numbers. References: X-Wing: Solving Sudoku : Technique 8 : X-Wing Web Sudoku - Billions of Free Sudoku Puzzles to Play Online -Evil Puzzle number 8,009,875,010. I noticed (I think!) the X wing to be present in the top middle box and bottom middle box. Top Middle Box: Bottom Left and Bottom Right Bottom Middle Box: Top Left and Top Right Numbers that fit were 1 and 9. (But neither of them properly implied the elimination of another number... The numbers implied that were to be eliminated left the area with the wrong number.) I hope this was not too confusing... THANKS!