Sudoku
Swordfish practice
A Swordfish is the three-line version of the X-Wing. A number is limited to the same three columns across three different rows. A row can use two or all three of those columns.
The three rows fill the three columns between them, so the number can be crossed off every other cell in those columns. As with the X-Wing, rows and columns can swap roles.
How to spot a Swordfish
Pick a number and list the rows where it has two or three places left. Look for three rows whose places add up to only three columns. It rarely looks like a neat grid, which is why it is easy to miss.
Practise it on this page
The board above deals positions where the Swordfish is the only way forward, with every pencil note filled in. Cross off the candidates it rules out and press Next. Press Hint to see the pattern marked on the board.
In a full game, Master is the first level that can ask for it.