"Last Digit" Sudoku technique explanation:

two sudoku puzzles demonstrating the last digit technique

Singles are the most basic and easy-to-understand techniques in solving sudoku puzzles. The Last Digit is the easiest and most understandable of them all.

It simply means the last digit that can be placed to correctly solve the Sudoku puzzle.

An example:

We can see that there is only one empty cell that remains in this number puzzle, it is marked with a blue square.

a sudoku board with a highlighted empty cell

Take a look at the house marked with the blue square, the only missing number in this house is 1, so 1 is the last digit.

sudoku solved by last digit technique

A house is a full set of numbers between 1-9 it can be a row, block, or column. If it is not the last digit, it is often called "Full House"