Full House
The last empty cell in a row, column or box. One cell, one missing digit, no thinking required.
What it is
A full house — also called a last cell — is a unit with eight digits already placed. The ninth digit is whatever is missing, and it goes in the one remaining cell. It is the simplest situation on the board and the first thing to check after every placement, because filling one cell often completes a neighbouring unit.
How to spot it
After you write any digit, glance along its row, its column and around its box. If any of them now has exactly one gap, fill it immediately. Chains of full houses are common in the endgame, where one placement cascades into five or six more.
Worked example
Step through the reasoning below. Each step adds one layer: first the position, then the pattern, then the candidates involved, and finally what can be eliminated.
Step 1 of 3: The starting position
- Pattern cells
- 6/2
- Digits
- —
- Eliminations
- —
Press a marked square to point it out on the board above.
Why it matters
Full houses cost no effort and keep the board moving. More importantly, they change the candidate landscape: each placement removes candidates elsewhere, which is often what turns a stuck position into a solvable one.
Practise now
Solve a puzzle where this technique decides the game
Frequently asked questions
Is a full house the same as a naked single?
Almost, but not quite. A full house is defined by the unit having only one gap. A naked single is defined by the cell having only one candidate. Every full house is also a naked single, but a naked single can appear in a unit with many empty cells.
When should I look for full houses?
Immediately after every placement. It takes two seconds and frequently starts a chain of easy placements, especially towards the end of a puzzle.
Put it to use
Where you will meet it
This pattern is the backbone of easy grids. Start one and you will use it within a few moves.
Play EasyStuck on a grid of your own?
Type the position into the solver and it walks the whole solution, naming the technique behind every step — including this one.
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