Intermediate Sudoku Techniques — Pairs, Triples and Pointing

Cubedoku Guides · Published 2026-06-10

There is a moment in every solver's progress where Easy puzzles feel automatic but Hard ones hit a wall: no cell has an obvious answer, scanning produces nothing, and it is tempting to guess. The gap is bridged by a family of techniques that share one insight — you can make progress by eliminating candidates, not just by placing digits. These four patterns handle the vast majority of intermediate positions.

Naked pairs (and triples)

Suppose two cells in the same row can each only be 4 or 7. You don't yet know which is which — but together they must consume both digits. Therefore no other cell in that row can be 4 or 7, and you may erase those candidates everywhere else in the row.

That is a naked pair: two cells in one unit (row, column or box) sharing exactly the same two candidates. The same logic scales to naked triples — three cells in a unit whose candidates collectively span only three digits. The eliminations a pair produces often create the next single immediately; pairs are the gateway drug of candidate logic.

Hidden pairs

The mirror image. Scan a box and ask: which cells can hold a 2? Which can hold a 9? If both digits fit in only the same two cells, those two cells are spoken for — they must contain the 2 and the 9 in some order. Any other candidates written in those two cells can be erased.

Hidden pairs are harder to spot than naked ones because the pair is buried under extra candidates — that is the “hidden”. The practical search habit: for each unit, count how many cells each digit can occupy. Digits confined to two cells are your raw material.

Pointing pairs

Now the interaction between a box and a line. Look at where a digit can go within one box. If all of its candidates in that box sit in a single row, then wherever the digit ends up, it occupies that row inside that box — so it cannot appear in that row in any other box. Erase accordingly.

This is a pointing pair(or triple): the candidates “point” along their line, projecting a constraint out of the box. It is the first technique where two different unit types cooperate, and it is everywhere once you start looking.

Box-line reduction

The same idea in reverse. If, within one row, a digit's only remaining candidates all fall inside one box, then the digit must live in that box-row intersection — so erase it from the rest of the box. Pointing pairs project out of a box; box-line reduction projects into it. Together they squeeze remarkable amounts of information out of partially solved regions.

How to actually use all this

Exhaust the basics first — hidden and naked singles from the beginner guide — they are faster when available.
When stalled, write candidates for the emptiest regions and hunt in order: naked pairs → hidden pairs → pointing pairs → box-line. The order runs from easiest-to-spot to subtlest.
After any elimination, re-check the affected unit for new singles before hunting more patterns. Eliminations exist to create placements.
Keep notes honest. Candidate techniques are only as sound as your bookkeeping — a stale candidate produces false deductions. (This discipline, more than any pattern, separates Hard solvers from Medium ones.)

Beyond pairs

These four patterns will carry you through Cubedoku's Hard difficulty on any grid size, and they transfer unchanged to the per-face logic of The Cube. Expert puzzles eventually demand multi-unit patterns — X-Wing, Swordfish, XY-Wing — covered in the advanced guide. But master pairs first: advanced patterns are pair-logic stretched across the whole grid, and they only feel natural once this layer is automatic.

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