Solving Sudoku : Forcing Chains
This technique (thankfully!) is quite easy to understand, but can take quite some time to work out within a puzzle. This is a technique where having a separate copy or notepad overlay really helps, because you’ll be making lots of notes!
A simple forcing chain is when you have lots of cells with just 2 candidates – and whichever value you would choose for one cell forces another cell to be just one of its two values. (It’ll be clearer with an example!)