2-String Kite
A 2-String Kite is a single-digit pattern built from two strong links in perpendicular houses — one row, one column. Each house has exactly two cells left for the candidate, and one cell from each pair shares a block. Because those two bridge cells see each other, they can't both hold the digit, which forces at least one of the other two endpoints to contain it — and that clears the digit from any cell seeing both.
What is a 2-String Kite?
A 2-String Kite is a single-digit pattern that joins two conjugate pairs sitting in perpendicular houses — one pair in a row, the other in a column. In each house the candidate digit appears in exactly two cells, so the digit must occupy one of them. The trick is that one cell from the row pair and one cell from the column pair land in the same block: they're the bridge, and because they see each other they can't both be the digit. That leaves the other two cells — one at the end of each strong link — carrying the consequence. At least one of them has to hold the digit, so any cell that shares a house with both of them can't.
How to spot it
2-String Kites don't announce themselves the way an X-Wing does, because the two strong links live in different directions — one horizontal, one vertical. The practical way in is to scan by digit: pick a candidate and look for rows and columns where it's down to exactly two cells. When you find a row pair and a column pair for the same digit, check whether one cell from each pair shares a block. If it does, you've got a kite, and the two cells that aren't in the bridge are your endpoints — anything seeing both of them loses the candidate. It's a quick check once you're already tracking conjugate pairs, and it shows up regularly in harder puzzles after the singles and subsets run out.
The logic
Every row and every column places each digit 1–9 exactly once. If a digit is confined to two cells in a row, exactly one of them holds it — a strong link. The same holds for a column. In a 2-String Kite, one cell from the row link and one from the column link share a block, so they can't both be the digit: a block can't contain two copies. That means at least one of the bridge cells is not the digit, which forces its partner in the strong link to be the digit. So at least one of the two non-bridge endpoints must contain the digit, and any cell that sees both endpoints — sharing a row, column or block with each — can't hold it. The pattern is a close cousin of the Skyscraper, which uses two parallel strong links instead of perpendicular ones.