All techniques
Locked Candidates (Pointing)
Working with Candidates11 / 32A box squeezes its digit into one line.
Inside a box, check where a digit can still go. If all of its candidates line up in a single row or column, the box will definitely place the digit on that line — it just doesn't know in which cell yet.
That's enough information to act on: the rest of the line, outside the box, can't have the digit. The candidates 'point' out of the box along the line.
See it in action
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Step 1 of 4
The setup
Go box by box, digit by digit: do the remaining candidates of a digit sit in one row or one column of the box? Step through this real position to see it happen.
Practice
Find the box whose digit is locked onto one line, and clear that digit from the rest of the line.
Drill 1 of 29Tap a cell, then the candidate digit you want to remove.