
Swordfish 

A Swordfish is where three columns have a candidate in only three different rows, or vice versa. This is like an XWing expanded into three units. The columns or rows that have these candidates are the primary units, and must only contain the candidates in the other three rows or columns called the secondary units. All other candidates in the secondary units can be eliminated.
Consider the example on this page. Rows 3, 5 and 9 only have 8's in columns C, E and H. Thus, all other 8's in columns C, E and H (highlighted in green) can be eliminated.
Sudoku Snake gives Swordfish a skill value of 75.






