Proven Sudoku
Unique Rectangle Type 5
Also called UR Type 5, UR5.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
Like Type 2, but the extra number sits in corners that sit across from each other rather than side by side. The reasoning is the same and so is the result.
The exact rule, for stronger players
The rule, stated exactly: A variant of Type 2 where the same extra digit z appears in two diagonally opposite cells rather than two adjacent ones. Then z is eliminated from cells seeing both.
What it removes: Remove z from cells seeing both z-bearing cells.
Why it works: Identical to Type 2. The diagonal arrangement does not change the argument, only the geometry. This technique is only valid when the puzzle is known to have exactly one solution. It is not a deduction about Sudoku rules, it is a deduction about the puzzle setter's promise. On a grid with multiple solutions it produces wrong answers.
Worked examples
None yet. This pattern does not turn up in our daily boards, so there is no real example to show. We would rather wait than draw a fake one.
Learn these first
- Unique Rectangle Type 2Two corners hold only the pair.
Related uniqueness
- Unique Rectangle Type 6Like Type 4, but the two numbers form an X across the rectangle instead of sitting along one side.
- Unique Rectangle with Missing CandidatesA rectangle where one corner has already lost one of the two numbers.
- Avoidable RectangleFour squares can form a rectangle across two boxes.
- Avoidable Rectangle Type 1Three corners of a rectangle were worked out by you, not printed in the puzzle.
- Avoidable Rectangle Type 2The same idea, but two corners are still open and share an extra number.
How often does it come up?
Our rough estimate: less common than Type 2. Some sources fold it into Type 2 rather than numbering it separately.