Cage Combination
Intermediate Removes candidates Used in: Killer Sudoku
A cage total often allows only a handful of digit combinations. A two-cell cage summing to 16 can only be {7,9}; one summing to 4 can only be {1,3}. Listing the legal combinations prunes candidates fast and frequently leaves just one digit per cell.
How to spot it
A cage whose total allows only a few digit combinations.
What you can conclude
Keep only candidates that appear in a legal combination; often just one survives.
Worked example
A two-cell cage totalling 16 can only be 7 and 9 — every other candidate goes.