Recognise the exact pattern
Choose one row, column or 3×3 box and inspect its candidate notes. A naked pair exists when exactly two unsolved cells in that unit contain the same two candidates and no others. If two cells in a row are both marked 2 and 7, those two digits must occupy those two cells in some order.
The cells do not need to sit next to each other. What matters is that they share one unit and that each cell contains only the same pair. Notes such as {2,7} and {2,7,9} are not a naked pair because the second cell still has a third possibility.
Keep the elimination inside the shared unit
Once a valid {2,7} pair is confirmed in a row, remove 2 and 7 from candidate lists in the other unsolved cells of that row. Do not remove them from unrelated cells elsewhere in the grid. The pair reserves both digits for its two cells only within the unit that proves the pattern.
If the same two cells also lie in one 3×3 box, the pair is valid in that box as well and the two candidates can be removed from the box’s other cells. That second elimination is justified because the pair shares both units, not merely because the cells are visually close.
Use a five-step check before erasing
First, name the unit: one specific row, column or box. Second, identify two cells in that unit. Third, confirm that each contains exactly the same two candidates. Fourth, check that the two digits are not already placed in the unit. Fifth, remove only those candidates from the unit’s other cells.
Say the reasoning in a complete sentence before changing the notes: ‘In row six, these two cells are both {3,8}, so 3 and 8 cannot appear in any other unsolved cell in row six.’ If the sentence cannot name one shared unit, pause—the elimination is probably not supported.
Look for the move the pair creates
The pair itself usually does not reveal which digit belongs in which of its two cells. Its value comes from what disappears elsewhere. After making the valid eliminations, rescan the affected unit for a cell with one candidate left or a digit that now has only one possible position.
Then update the intersecting row, column and box after every confirmed placement. A pair may produce a single, that single may open another box, and the original pair can remain unresolved until much later. Do not guess the order of the pair merely to keep moving.
Avoid three common false pairs
Two cells that merely share two candidates are not enough if either cell has additional candidates. Three cells containing only the same two digits are also not a naked pair; recheck the notes, because three different cells cannot all be filled by only two digits. Finally, identical pairs in different units cannot be combined unless the cells themselves share the unit where the elimination is made.
Stale candidate notes are another source of mistakes. Before declaring a pair, compare both cells with all placed digits in their row, column and box. Remove contradicted notes first, then evaluate the pattern using the cleaned candidate lists.
Practise the technique deliberately
Open Daily Sudoku and begin with normal scanning. Add candidates only when forced placements stop appearing, then inspect units with relatively few unsolved cells. These smaller candidate sets make genuine pairs easier to distinguish from coincidental overlaps.
When you find one, record the unit, the two cells, the paired digits and the eliminations it permits. Use Check progress after the resulting logical sequence rather than after every mark. The goal is not to hunt pairs in every grid; it is to recognise the pattern accurately when the current puzzle makes it useful.