Grid technique · Advanced
Locked Pair
When two items are each confined to the same two subjects, those two subjects are used up between them, so everyone and everything else is excluded from both.
Why it works
Two items, two possible homes between them, no room for a third. The pair doesn't have to be resolved to know that nobody else can have either one.
Trigger
Two rows (or columns) in the same mini-grid, each narrowed to exactly the same two candidates.
Common mistake
Waiting to know which of the two subjects gets which item before eliminating everyone else — the elimination is valid before that is decided.
Example
If both the llama and the cat are narrowed to just Mina or Theo, then everyone else is excluded from both, regardless of which pet ends up with which person.