Lesson 22

Grouped Two-String Kite

The rule

When a row and a column each have a number as a candidate only in one far cell outside a shared box and a group inside it, and the two groups share no cells, the box can satisfy at most one group, so at least one far end must hold that number, and any cell seeing both far ends loses that candidate.

Step by step

1. For 2, the outlined row and column each hold that candidate in only one far cell plus one or more cells inside the shared box. Each line is a strong link between its far end and its box group, and the box can hold 2 only once, so the two groups cannot both take it. This is a Grouped Two-String Kite!
2. If either far end were not 2, its line would push 2 into its box group, and the box would then force the other line onto its far end. At least one far end must be 2, so we can remove the candidate 2 from the red cell that sees both far ends.