Tier 2 · first asked for by Moderate
Naked Pair
Two cells in a unit sharing the same two candidates lock those digits away.
Also called Naked Twins, Conjugate Pair.
Find two cells in the same row, column or box that each hold exactly the same pair of candidates — say 3 and 7, and nothing else. You do not know which is which, but between them they use up both digits.
That means neither 3 nor 7 can appear anywhere else in that unit, and both can be crossed off every other cell in it. The pair is called naked because the two digits are written plainly in the cells, with nothing else to hide behind.
A worked example
A real position, with the pencil marks a solver would have at that point.
the pattern · what it rules out · 5 a candidate that goes
What it proves. R1C4, R2C4 in column 4 hold only 4/8 between them, so those digits leave the rest of the column.