Practise: Almost Locked Sets (ALS-XZ)
This verified teaching position begins directly with a real Almost Locked Sets (ALS-XZ) pattern. Follow the chain, inspect the candidates and make the deduction before you continue.
You are at the verified key position. Use a hint to follow the chain link by link when you need support.
How to spot it
Look for two to four cells in a row, column or box whose combined candidates are exactly one more than the number of cells. Compare disjoint sets for two shared digits. One shared digit must occur once in each set and its two cells must see each other; that is the restricted common candidate. Then inspect external cells that see every occurrence of the other shared digit.
Put it to use
Where you will meet it
Expert grids are the only place this pattern regularly decides the solve. Bring your notes.
Play ExpertStuck on a grid of your own?
Type the position into the solver and it walks the whole solution, naming the technique behind every step — including this one.
Open the solverPrefer paper? Ready-made Expert sets as a PDF.Print puzzles