{"id":521,"date":"2025-12-17T12:46:33","date_gmt":"2025-12-16T23:46:33","guid":{"rendered":"https:\/\/thesudoku.com\/blog\/?page_id=521"},"modified":"2026-07-24T16:45:08","modified_gmt":"2026-07-24T04:45:08","slug":"claiming","status":"publish","type":"page","link":"https:\/\/thesudoku.com\/blog\/claiming\/","title":{"rendered":"Claiming"},"content":{"rendered":"\n
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< Back<\/a><\/p>\n<\/div>\n\n\n\n

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How to Use the Claiming Pairs Strategy (Box-Line Reduction)<\/p>\n\n\n\n

To solve hard Sudoku puzzles<\/strong><\/a> efficiently, you must learn to see the grid from multiple angles. The Claiming Pairs technique<\/strong> (also known as Box-Line Reduction<\/em>) is a brilliant intermediate strategy.<\/p>\n\n\n\n

While the Pointing<\/em> strategy uses a 3×3 block to clear out a row or column, the Claiming strategy does the exact opposite: it uses a single row or column to eliminate useless pencil notes inside a 3×3 block.<\/p>\n\n\n\n

Claiming applies when a candidate appears only in one box within a row or column.<\/strong> When a line claims a number like this, it cleans up the entire neighboring square.<\/p>\n\n\n\n

The Logic Behind Claiming Pairs<\/strong><\/h2>\n\n\n\n

Every single row and column across the 9×9 Sudoku grid must contain the numbers 1 through 9. As you scan a long line of pencil notes, you will sometimes notice that a specific candidate is heavily restricted.<\/p>\n\n\n\n

Take a look at this example. <\/p>\n\n\n\n

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\"An<\/figure>\n\n\n\n
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All the remaining options for the number 2 on this line happen to sit inside the same 3×3 block<\/strong>. Because the row must<\/em> have the number 2 somewhere, and it has no other places left to go, we reach a logical certainty: 2 must definitely be placed in one of these cells.<\/strong><\/p>\n\n\n\n

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\"Claiming<\/figure>\n\n\n\n
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The Power of Elimination (Step-by-Step)<\/strong><\/h2>\n\n\n\n

Once you realize that the row has locked the number 2 into that specific block, you can use this information to clear out the surrounding cells inside that square:<\/p>\n\n\n\n

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  1. Scan the line:<\/strong> Look closely down a full row or column and find a candidate (like 2) that only appears within the boundaries of a single 3×3 block.<\/li>\n\n\n\n
  2. Lock the region:<\/strong> Recognize that this row has “claimed” that space for the number 2.<\/li>\n\n\n\n
  3. Clean the rest of the block:<\/strong> This means that 2 can\u2019t appear anywhere in the box outside the row.<\/strong><\/li>\n<\/ol>\n\n\n\n
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    \"Results<\/figure>\n\n\n\n
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    Because the target row is guaranteed to place its 2 inside that block, no other<\/em> row crossing through that same block can possibly claim a 2. Therefore, you can safely delete the number 2 from the pencil notes of all other empty cells inside that 3×3 block that do not belong to your original row.<\/p>\n\n\n\n

    Claiming Rows vs. Claiming Columns<\/strong><\/h2>\n\n\n\n

    This strategy is incredibly versatile and can be spotted in two ways:<\/p>\n\n\n\n