Medium

Claiming

What it is

If a digit in a row or column can only go inside one box, it can be removed from the rest of that box.

How to spot it

Look along a row or column: are all candidates for one digit in the same box? Then the digit is in that part of the line, and the other cells of the box can't hold it.

Example

Basis
Removed / placed

In row 1, 6 can only go in r1c2 or r1c3, both in box 1. So 6 can be removed from the other cells of box 1: r2c1 and r3c2.

Used from level: Medium