How to solve locked candidates (pointing and claiming) in Sudoku
Locked candidates remove a digit from a row, column or box when all of its remaining spots in another unit line up.
How it works
Pointing: if every place a digit can go in a box lies in one row (or column), then the digit is sure to be in that row inside the box. So it can be removed from the rest of that row outside the box.
Claiming is the same idea turned around: if every place a digit can go in a row (or column) lies inside one box, the digit must be in that box, so it can be removed from the other cells of the box.
How to spot it
Look at a box where a digit has only two or three spots left, all in a line. Then check the rest of that line for the same digit, which can be removed.
A worked example
This is a step from a real puzzle, a moment where the next move needs locked candidates (pointing and claiming).
Struck-through digits are the ones that can be removed.
In box 1, 8 can only go in row 3, so it can't appear elsewhere in that row. Remove 8 from R3C4, R3C5, R3C6.
Where it fits in Rocksled Sudoku
Puzzles that need locked candidates (pointing and claiming) are never rated below Medium. Each step of this kind adds 10 points to a puzzle’s difficulty score. When you ask for a hint that needs it, the game names the technique and shows the cells involved. See how to play for the rest of the controls.