Finned X-Wing
Short answer: you found an X-Wing except that one of its lines has an extra cell. If that extra cell — the fin — is in the same box as part of the pattern, then either the X-Wing is real or the fin holds the shape. Both put the shape in that box, so the elimination survives there and nowhere else.
What a finned X-Wing looks like
Every solver has abandoned an almost-X-Wing. Two lines, the shape confined to the same two crossing lines in both, except for one stubborn extra cell — so you move on. That is the wrong move surprisingly often. The near-miss is worth something, provided the extra cell is somewhere specific.
The reasoning is a case split you never have to resolve. If the fin is not the shape, the pattern is a plain X-Wing and clears both crossing lines entirely. If the fin is the shape, then that box has its shape. The elimination is whatever both cases agree on: cells in the crossing lines that are also in the fin's box.
How to use a finned X-Wing
- Find the near-miss. Look for what you would call an X-Wing except that one of the two lines has a third possible cell for the shape. Do not discard it — note where that third cell is.
- Check the fin shares a box. The fin must sit in the same box as the pattern cell it is nearest to, in the same base line. If the fin is off in an unrelated box, there is no elimination and you really should move on.
- Work out where the two cases overlap. A plain X-Wing would clear both crossing lines; the fin being true would fill its box. The overlap is the cells that are in a crossing line and in the fin’s box — and are not part of the pattern.
- Strike only that overlap. Remove the shape from those cells and nothing else. Striking the whole of both crossing lines is the classic error here: that only follows if the fin is false, which you have not shown.
Two fins are allowed as long as they are in the same box — the argument only needs "if the pattern fails, the shape is in this box". A near-miss where the extra cell is in a different box is genuinely worthless, but check the other orientation before giving up: a skyscraper or two-string kite often lives in the same position.
Finned X-Wing vs X-Wing
A plain X-Wing clears both crossing lines completely; a finned one clears a corner of them. That makes it sound weaker, and per instance it is — but finned X-Wings are roughly as common as clean ones, so learning the repair roughly doubles how often the pattern pays out. It also changes how you scan: instead of discarding near-misses you start asking where the extra cell is, which is a much more productive habit.
Find Finned X-Wing in your own grid
Paste a puzzle and this page will look for Finned X-Wing in it — the same pattern shown above, in your grid instead of ours. Nothing is uploaded; it runs in your browser.
Frequently asked questions
What exactly is a fin?
The cells that spoil the pattern — the ones in a base line that fall outside the crossing lines. There can be one or two, but they must all be in a single box, because the whole argument is "if the pattern is false, this box holds the shape".
What is a sashimi fish?
A finned fish where one of the base lines does not even reach every crossing line — the pattern has a hole in it as well as a fin. The reasoning is unchanged and so is the elimination, which is why this page does not treat it as a separate technique.
Why can I not strike the whole column?
Because you have not ruled the fin out. Striking the whole crossing line assumes the X-Wing is real, and all you have shown is that either it is real or the fin holds the shape. Only the cells covered by both cases are safe, and those are the ones inside the fin’s box.
Do fins work on bigger fish?
Yes, identically. A finned Swordfish and a finned Jellyfish are the same repair at size three and four, and finned versions are more common than clean ones as the fish gets bigger.