"Locked Candidates" Sudoku solving technique explained:

locked Candidates sudoku demonstration

As you probably came to understand, there are two types of locked candidates techniques. Both techniques work in the form of elimination but each one is a bit different.

Locked Candidates 1

If in a block all candidates of a specific number are bound to a row or column, that number cannot appear outside of that block in that row or column.


locked Candidates 1 sudoku example

Locked Candidates 2

Locked candidate 2 works in the opposite way: If in a row (or column) all candidates of a certain digit are confined to one block, that candidate is eliminated from all other cells in that block.

sudoku example for locked Candidates 2