Pointing Pairs

A Pointing Pair is the box-to-line direction of Locked Candidates.

Inside one 3×3 box, every remaining position for a digit lies on the same row or column. The exact cell is still unresolved, but the box has proved something useful:

This digit must appear on this line inside the box.

Therefore the same candidate can be removed from that line outside the box.

Although Pointing Pair is the familiar name, the same proof can involve three aligned source positions. Pointing Candidates is the more general description.

Pointing Pairs at a glance

Start with a box.

If all candidate Xs in that box lie on one row:

remove X from that row outside the box.

If all candidate Xs in that box lie on one column:

remove X from that column outside the box.

Direction: box → line.

Why Pointing works

Suppose box 5 still needs digit 7.

Inside the box, 7 can appear only in r4c4 or r4c6.

Both cells lie on row 4.

One of those two cells must eventually contain 7 because box 5 requires a 7. So row 4 is guaranteed to receive its 7 somewhere inside box 5.

That means any candidate 7 on row 4 outside box 5 is impossible.

Notice what has not been proved:

• r4c4 = 7 is not known;
• r4c6 = 7 is not known.

The weaker statement is enough:

row 4's 7 is inside this box.

That is the entire Pointing proof.

Step-by-step row example

When checking a Pointing example, separate the source positions from the elimination targets:

1. identify the source box;
2. find every legal position for the digit in that box;
3. confirm that all source positions share one row;
4. keep the source candidates;
5. remove the digit only from the same row outside the box;
6. re-scan the affected line.

Pointing can run down a column

The pattern is completely symmetric vertically.

If every candidate 4 in a box lies in column 8, the box must place 4 somewhere in column 8.

Candidate 4 can therefore be removed from column 8 outside that box.

Pointing Pair vs Pointing Triple

Suppose a box can place digit 2 only in:

• r8c4;
• r8c5;
• r8c6.

All three cells lie on row 8.

The box still guarantees that row 8 receives digit 2 inside the box, so other candidate 2s on row 8 outside the box can be removed.

Some resources call this a Pointing Triple.

It is not a different proof. The general condition is simply:

all remaining positions for one digit in the box share one line.

The number of source positions is secondary.

The source candidates must be complete

Pointing is valid only if the highlighted cells are all legal positions for the digit inside the source box.

If another candidate X exists in a different row or column of the box, the box is no longer locked to one line.

This is why a candidate filter can be so useful. It lets you verify the complete positional pattern instead of relying on a partial visual impression.

Where can Pointing eliminate?

The target area is precise.

For a row-based Pointing pattern:

• keep every source X inside the box;
• inspect the shared row;
• remove X only from cells on that row outside the source box.

For a column-based pattern, do the same vertically.

Pointing does not remove X from arbitrary peers of the source cells. The elimination comes from the shared line constraint.

Why Pointing is a natural extension of Crosshatching

Crosshatching already trains you to follow one digit through a box.

Beginner outcome:

restrictions leave one possible cell.

→ Hidden Single.

Intermediate outcome:

restrictions leave several possible cells, but all of them share one row or column.

→ Pointing.

This is why Pointing often feels like advanced scanning rather than an entirely new kind of reasoning.

How to find Pointing Pairs faster

Pointing is a digit-first search.

1. Choose a digit

A digit with several solved copies can be easier to scan because many lines are already blocked.

2. Inspect boxes that still need the digit

Identify every legal candidate position inside each box.

3. Look for alignment

Ask whether all remaining positions share:

• one row;
• or one column.

4. Inspect the line outside the box

The pattern is productive if the same candidate appears elsewhere on that line.

5. Re-scan after the elimination

A Pointing move can create:

• a Hidden Single;
• a Naked Single;
• another Locked Candidates pattern;
• a subset.

Pointing vs Hidden Single

Both can begin by inspecting one digit inside a box.

Hidden Single

Only one legal cell remains.

→ Place the digit.

Pointing

Two or three legal cells remain, but all are on one line.

→ Eliminate the digit from that line outside the box.

Pointing is therefore a partial positional solution: the exact cell is unknown, but the line is known.

Pointing vs Claiming

These techniques use the same box-line intersection in opposite directions.

Pointing

The source restriction is proved inside the box.

box → row/column

Claiming / Box-Line Reduction

The source restriction is proved inside the row or column.

row/column → box

If the highlighted geometry looks similar, ask:

Which house did I inspect first to prove where the digit must go?

That is the source house, and it tells you which direction you are using.

Pointing vs a solved placement

Pointing normally removes candidates rather than placing a digit.

Do not choose one of the source cells just because the pattern is strong. The source positions remain alternatives until some later deduction distinguishes them.

The value of the move is the elimination it creates elsewhere.

Common mistakes

Removing the digit from the source positions

Those positions must remain. They are the reason the box guarantees the digit on the shared line.

Missing a third source candidate

If another legal X exists in a different line of the box, Pointing is not established.

Searching only for two-cell patterns

Three aligned source positions use the same proof.

Eliminating from the wrong line

The elimination follows the row or column shared by all source candidates.

Treating partial notes as a complete candidate map

Selective notes can hide a legitimate source position. Verify the logic from the grid if your notes are incomplete.

Expecting a placement

The direct result is usually candidate elimination.

Recognition drill

With one candidate digit highlighted, ask this exact question in every box:

“Does this box's X live on one line?”

If yes, look along that line outside the box.

That question is short enough to become part of a normal intermediate scan.

FAQ

Why is it called a Pointing Pair?

The candidate positions inside the box visually point along their shared row or column toward candidates that can be eliminated.

Is Pointing Pair the same as Locked Candidates Type 1?

Yes. That is a common solver name for the same box-to-line direction.

Do the source cells need to be adjacent?

No. They only need to be in the same box and on the same row or column.

Can Pointing use three candidates?

Yes. A three-cell version is often called a Pointing Triple, but the logic is identical.

Is Pointing possible without pencil marks?

Yes. You can calculate the remaining positions mentally. Complete candidate displays or digit filters simply make verification easier.

Is a Pointing Triple harder than a Pointing Pair?

It may be slightly harder to notice, but the logical proof is the same.

What to learn next

Learn Box-Line Reduction / Claiming to reverse the direction of the same intersection logic.

Then continue to Naked Pairs, where the restriction changes from one digit trapped in an intersection to two digits reserved for two cells.