Intersections

Intersections use the overlap between a row or column and a block. If a digit is locked into that overlap, it can be removed from the rest of the other house.

When to look for it

Look for one digit whose candidates in a block are all in one row or column, or whose candidates in a row or column are all in one block.

Implemented in Xodoku

Locked Candidates: Pointing

If all possible locations for a digit in a block are in one row or column, that digit cannot appear elsewhere in that row or column.

Locked Candidates: Claiming

If all possible locations for a digit in a row or column are inside one block, that digit can be removed from the rest of the block.

Rule

Both forms rely on the same idea: the digit must be placed somewhere in the intersection, so candidates outside the intersection but inside the affected house are impossible.