Unique Rectangle Type 2
This deduction assumes the puzzle has exactly one solution and that all earlier candidate removals were sound. This Type 2 Unique Rectangle deduction starts from a candidate arrangement whose two-value swap would preserve every affected row, column, and box. Extra candidates or a link restriction prevent that deadly swap and justify only the stated elimination.
What is Unique Rectangle Type 2?
This deduction assumes the puzzle has exactly one solution and that all earlier candidate removals were sound. First verify the complete two-value structure and every sector it touches. The swap must move no given and must leave each affected sector with one occurrence of each base digit. Type 2 then uses its additional candidate condition; an arbitrary rectangle or even cycle is not enough.
Type 2 uses the additional condition described below to prevent the verified two-value exchange. The conclusion may be inside the rescue cells or in their common peers; apply only the target rule for this type.
How to spot it
Verify four unsolved corners in two rows, two columns, and exactly two boxes. The rescue cells share an extra digit, and they share a sector or otherwise give the proposed target visibility to every rescue occurrence. The extra digit is true in at least one rescue cell, so remove it only from candidates seeing all of them.
The logic
If no rescue cell used the shared extra digit, the complete deadly swap would remain. Therefore at least one rescue cell uses the extra digit, and a candidate seeing every possible rescue occurrence cannot use it.