Box-line mastery
Pointing & Claiming: Remove Dozens of Candidates in a Single Pass
Pointing pairs and claiming lines (also called box/line reduction) force candidates out of entire regions. Use this tactic when naked pairs stall out and the grid feels clogged. The Pure Sudoku interface lets you toggle notes fast so these eliminations never get messy.
Pointing pairs explained
When a candidate is restricted to a single row or column inside a 3×3 box, it can’t appear elsewhere along that line. Delete the candidate from every other cell in that row or column. Repeat after every placement to prevent stale notes.
Claiming lines explained
Flip the logic: if a row or column contains a candidate that only lives in one box, then the rest of the box cannot use that digit. Clearing those cells often creates hidden singles or fresh pairs to explore.
Interactive play-by-play
Pointing and claiming on the same box
Scrub through the mini board to see a pointer remove a digit from a row and a claimer finish the column.
Step 1
Pointer locks a row
Digit 5 only exists in the top row of this box. It must live in one of those highlighted cells.
Step 2
Remove the digit elsewhere in that row
The rest of the row (gray cell) can’t hold a 5 anymore. That’s the pointing pair effect.
Step 3
Claiming locks the box
The column now has a single 5 left inside this box, so you place it immediately and continue scanning.
Step 1 of 3
Drill: The box sweep
- Pick a hard puzzle and fill all candidates.
- Check each box for numbers that sit exclusively in one row/column.
- Eliminate them elsewhere and repeat on rows/columns for claiming.
- Document how many singles emerge after every sweep.
The Pure Sudoku undo stack makes experimentation safe—roll back if you eliminate the wrong digit and learn from the attempt.