The counterpart to a hidden single is the naked single. These are a little harder for me to spot.
When a square’s three containers cumulatively contain 8 different digits, this leaves only one possible value, via the process of elimination, the naked single. The question mark below is a naked single.
I find that naked singles more frequently come into play when I am finishing up the last few squares of a puzzle, but the pattern is usually present in the beginning, if you are observant.
After I exhaust the obvious hidden singles, I’ll start looking for naked singles, and there are usually one or two in plain sight. Good candidate squares are ones that contain a lot of numbers in their containers, like the green square above.
Here’s a sample puzzle where there are 7 naked singles. I’ve highlighted two of them.
What numbers must they be?
Can you find the others?