How to read the grids
- Given - clues from the starting puzzle
- Subject - cells the technique focuses on
- Eliminated - candidates this technique removes
- Candidate - pencil marks shown for reference
How to spot it
Spot four cells forming a rectangle that all have the same {X, Y} candidate pair. The technique forbids the configuration; identify which extra candidate must remain to break the symmetry.
3
6
3
6
3
6
3
6
8
Worked example
Four cells in two rows / two columns all pencil {3, 6}. The fourth cell also pencils 8. Since the all-{3,6} configuration would create two solutions, 3 and 6 are eliminated from the fourth cell - it must be 8.
Time to practice
Reading is half the work. Try a puzzle now and look for the techniques you just learned.