Locked Set

For a set of cells in the same unit that contain a group of candidates, when the number of cells in the set and the number of candidates in the group is the same, the set of cells is considered a Locked Set.

A Locked Set has the following properties -

• 1. The cells in the set will end up containing one of the group of candidates.
• 2. The candidates in the group cannot be used in other cells in the unit because they will all be used in the cells in the set.

A Naked Pair is an example of a locked set.

An Almost Locked Set is a set of cells in the same unit where the number of candidates in the set is one more than the number of cells.The blue cells in Figure 1 are an example of a Locked Set in box 2 using the candidates 1 and 6.The blue cells in Figure 2 are a Locked Set in row 6 using the candidates 3, 4 and 9.