How to Solve Sudoku: 2-String Kite

A row and a column where a digit has only 2 places, joined inside one box. Then the digit can be removed from any cell that sees both of the remaining 2 ends.

Also called simply a Kite. On Puzzle Lounge it appears at Master.

See it step by step

  1. A board full of notes. Look only at the 4s (the small digits are the notes, or candidates)
  2. ● = a cell where 4 can go (notes other than 4 have been removed)
  3. In row 8, 4 has only 2 places
  4. Column 4 also has only 2 places (the 2 lines are joined in the box below)
  5. 4 can only go in these 3 ways (it cannot be in both of the 2 cells inside the box)
  6. In every case, one of the remaining ends is 4 (row 8, column 2 or row 1, column 4)
  7. So a 4 that sees both ends can be removed (4 goes from row 1, column 2)

This is Master No.1, partly solved.

Solve this puzzle →

How to find it

  1. Pick a digit and list the rows and columns where it has only 2 candidates.
  2. Find a row and a column where one end of each falls in the same box.
  3. Look at the cell that sees both of the remaining 2 ends (where the row end's column meets the column end's row).

Things to watch

  • The 2 ends inside the box must be separate cells.
  • Usually you can remove it from just one cell. Look where the row end's column meets the column end's row.
Read the full explanation

When a digit has only 2 candidates in a row and only 2 in a column, and one end of each falls in the same box, the digit must be in one of the remaining 2 ends. So it can be removed from any cell that sees both of those 2 ends.

Suppose a digit (say 4) can go in only 2 places in row A and only 2 places in column X. One end of row A and one end of column X are in the same box.

The 2 cells in that box cannot both be 4. If row A's 4 is not inside the box, the other end of the row is 4; the same goes for column X. So one of the 2 ends outside the box must be 4.

So 4 cannot go in any cell that sees both of those 2 ends. The name comes from the shape, like a kite with 2 strings tied at the box.

4 can go only in the 2 places row 8, column 5 and row 8, column 2, and the 2 places row 7, column 4 and row 1, column 4. Row 8, column 5 and row 7, column 4 are in the same box, so they cannot both be 4. So one of row 8, column 2 and row 1, column 4 is 4, and 4 can be removed from the candidates at row 1, column 2, which sees both.

Other techniques

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For the basics and how to use notes, see how to solve sudoku, with tips. If you get stuck, the game's hints guide you step by step, starting with where to look.

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