| Sudoku Tutorial |
| Naked Quads |
| When a house has four cells which contain
only combinations of the same four numbers, those are Naked Quads. In column 3, the yellow cells all contain only 3,4,5, and 8. That means that the 3458 cannot exist in any other cells of that house (column 3). Column 3 also has a hidden quad (click here to see it)  |