Solving Sudoku : Swordfish
This is very similar to using X-Wings, in that it will allow you to use knowledge about rows to remove candidates from columns, and vice versa.
Make sure you’re happy with why X-Wings work before moving on to Swordfish!
The complexity here is that you’re using knowledge from 3 rows at the same time – and that’s what makes them harder to spot. Unlike X-Wings, they don’t form a simple rectangle.