Grid technique · Intermediate
Set Transposition
The locked-pair idea applied across categories: if a locked pair in one mini-grid lines up with a locked pair in another, the two pairs' possible subjects are the same set.
Why it works
If two items are confined to exactly the subjects holding a locked pair, their subject sets are identical to that pair's, so an elimination against one pair transfers straight across to the other.
Trigger
A locked pair in one mini-grid, plus a second pair of items in another category confined to the exact same two subjects.
Common mistake
Treating the two mini-grids as unrelated once the first locked pair is found, instead of checking whether a second category is locked to the same two subjects.
Example
If price is locked to Mina/Theo, and colour is separately locked to Mina/Theo, an elimination against one price-holder eliminates the matching colour too.
On Bambleweeny's board
Confirmed in the live solver as the k=2 case of this technique. A generalised k>2 version was investigated and found to add nothing new — Two-Bridge Elimination already reaches the same conclusions first.