4-cell killer cage summing to 10
Single combination — fully locked1 combination.
- Always present
- 1234
- Never present
- 56789
Valid digit combinations
- 1234
How to use this in play
A 4-cell killer cage of 10 is fully locked: the only way to make 10 from 4 distinct digits is {1, 2, 3, 4}. Whatever order they sit in, those digits are the cage's contents — every one of them eliminates from every cell of the cage's row, column, and box that lies outside the cage.
Locked digits: 1, 2, 3, 4. Whichever combination is in play, these digits sit somewhere inside the cage — meaning the cage's shared row, column, and box can't have any of them anywhere outside the cage.
Forbidden digits: 5, 6, 7, 8, 9. These digits never appear in this cage no matter which combination resolves; you can eliminate all of them from every cell of the cage as you pencil in candidates.