Pointing Pair/Triple
A digit confined to one row or column within a box is eliminated from the rest of that line.
How it works
- 1Inside one box, find a digit whose remaining cells all sit in a single row (or column).
- 2The box must contain that digit somewhere, so it lands in that row within the box.
- 3The digit is therefore impossible in the rest of that row outside the box — strike it there.