A naked pair is two cells in one row, column or box whose complete candidate sets are the same two digits. Those digits can be removed from other cells in that unit.
The pair reserves two digits, not their order
Suppose two cells in a row both have exactly {3,7}. One must become 3 and the other 7, although their order is not yet known. Another cell in the row with {3,7,9} therefore reduces to 9. The deduction fails if either supposed pair cell still allows another digit. Rebuild doubtful notes from the row, column and box before relying on them; two similar-looking notes are not enough.
Try the steps
- Choose one row, column or box and identify two cells with exactly the same two candidates.
- Remove those digits from other cells in that unit, without filling either member of the pair yet.
- Check for new singles, then update all affected notes after any confirmed placement.
Can a row pair also eliminate digits from its boxes?
Only from a box containing both pair cells. If they occupy different boxes, the row deduction does not reserve both digits inside either box. Every elimination needs a shared unit; do not extend the pattern to unrelated cells just because their notes contain the same digits.