Locked Candidates: Step-by-Step Guide
When a digit’s candidates in a 3×3 box all sit in one row or column, eliminate that digit from the rest of that row/column (pointing). Conversely, if a row/column’s candidates for a digit are confined to one box, eliminate the digit from the other cells in that box (claiming).
Prerequisites
How to recognize it
- Pointing: All candidates for a digit in a box lie in a single row or column.
- Claiming: All candidates for a digit in a row/column lie inside one box.
Why it works
If a digit must occupy a specific line within a box, that line’s other boxes cannot contain that digit. Symmetrically, if a line’s candidates all fall in one box, that box’s other lines cannot contain the digit.
Try it now
Interactive example coming soon: highlighting a pointing or claiming pattern with one-click eliminations.
Common pitfalls
- Confusing “all in one line” with “mostly in one line”. Every candidate must be on that single line.
- Forgetting the symmetric nature of pointing vs. claiming.
Related: X-Wing