GridWits
Hard tier Technique 10 of 20 Used by Smart Hint

Locked Comparison

A high digit is locked into cells that each point through an inequality to the same forced larger digit — that larger digit is locked into the partner cells and can be removed from every cell seeing them all.

How it works

  1. 1In row 1, digit 4 is locked into columns 1, 3 and 5.
  2. 2Each possible 4 is below a neighbour whose only value above 4 is 5. Wherever row 1 puts its 4, the matching cell in row 2 must therefore be 5.
  3. 3Row 2 column 2 sees all three possible partner cells through its row, so it cannot be 5.
  4. 4The mirrored form is also valid: if every home of a digit is above a neighbour forced to one smaller value, that smaller value is locked into the neighbours.
1 4 1 2 3 5 2 4 1 2 3 5 3 4 2 5 1 2 5 1 5 3 5 ∧ ∧ ∧
  • Candidates this technique rules out
  • Smaller → larger — The arrow follows the direction imposed by the inequality sign.
  • Cells read together — The connecting line shows which cells combine to make the deduction.
  • Conclusion — The coloured candidate, or the final arrow when it lands outside the pattern, shows the result.
Next in the ladder X-Wing →

A value's only two candidate cells line up in the same two columns (or rows) across two rows (or columns) — eliminate it everywhere else in those columns or rows.