The 2-String Kite is an advanced Sudoku technique that uses two conjugate pairs for the same candidate digit connected through a shared box. Unlike a Skyscraper, where the two conjugate pairs share a row or column, in a 2-String Kite one conjugate pair lies along a row and the other along a column, with one cell from each pair residing in the same box. This box connection acts as the joint of the kite.
The pattern works as follows: one conjugate pair is in a row (cells A and B), and the other is in a column (cells C and D). Cells B and C share the same box, creating the strong link between the two pairs. The two endpoints that do NOT share the box are cells A and D — the "tips" of the kite. The logic is identical to a Skyscraper: the candidate must appear in at least one of the two unlinked tips. If A does not contain the digit, then B must (conjugate pair in the row), which means C cannot (same box exclusion), which forces D. The reverse holds symmetrically. Therefore, any cell that can see both tips A and D can have the candidate eliminated.
The 2-String Kite is a close relative of the Skyscraper and Turbot Fish. It is often overlooked because solvers tend to scan only rows or only columns for conjugate pairs, missing the row-column combination connected by a box. Once you learn to look for this cross-shaped connection, you will find 2-String Kites appearing frequently in hard puzzles, often providing the key breakthrough where fish and wing techniques stall.
Try It Yourself
Walk through each step of the 2-string kite technique on a real puzzle. Follow the instructions and try entering the correct value when prompted.
We are looking for a 2-String Kite on candidate 8. In row 4, candidate 8 appears in exactly two cells: (3,3) and (3,7), forming a conjugate pair. In column 4, candidate 8 appears in (3,3) and (7,3), forming another conjugate pair.
Step-by-Step Guide
Choose a candidate digit and find all conjugate pairs in rows, columns, and boxes.
Look for a conjugate pair in a row and a conjugate pair in a column where one cell from each pair shares the same box.
Identify the two unlinked tips: the cells from each pair that are NOT in the shared box.
Recognize that the candidate must appear in at least one of the two tips.
Eliminate the candidate from any cell that can see both tips simultaneously.
Re-evaluate the grid for new singles or further patterns.
Think of two sticks connected by a box — push one end and the other end must move, so anything caught between both far ends gets swept away.
The row strong link and the column strong link each independently enforce a binary choice for the digit. The box where one cell from each link coexists acts as a mutual-exclusion constraint: both hinge cells cannot hold the digit simultaneously because they share a box. This creates an implication chain from tip to tip — falsifying one tip forces its conjugate partner (the hinge cell), which excludes the other hinge cell via the box constraint, which forces the opposite tip true. Therefore at least one tip must always contain the digit.
When to use: Use 2-String Kite when you spot a candidate with a conjugate pair in a row and another conjugate pair in a column, where one cell from each pair shares the same box. It works when Skyscraper fails because the pairs are not in parallel rows or columns.
Common Mistakes to Avoid
Requiring the two conjugate pairs to be in parallel rows or parallel columns.
A 2-String Kite specifically needs one pair in a row and one pair in a column, joined through a shared box. Parallel pairs form a Skyscraper instead.
Using the box-connected cells as the elimination targets instead of the unlinked tips.
Eliminations target cells that see both unlinked tips (the cells NOT in the shared box). The box-connected cells are the hinge, not the targets.
Forgetting that the box connection must be a strong link — the candidate can only appear in those two cells within the box intersection.
The box does not need to be a conjugate pair. The connection works because the row-pair and column-pair each independently force their cells, and the box prevents both hinge cells from being true.
More Examples
See 2-string kite applied in different puzzle configurations to strengthen your pattern recognition.
2-String Kite on Digit 9
Highlighted cells show the 2-string kite pattern
Practice Puzzles
Apply the 2-string kite technique on these mini challenges. Tap a highlighted cell and enter the correct digit.
Quick Reference
- Pattern:
- A candidate has conjugate pairs in a row and a column, connected through a box
- Action:
- Eliminate the candidate from cells that see both unconnected endpoints
- Look for:
- Row and column conjugate pairs linked through a shared box