GridWits
Easy tier Technique 1 of 21 Smart Hint: Skyscrapers and Skyscrapers+

Naked Single

Only one candidate height remains for this cell — place it.

How it works

  1. 1Heights 1 to 4 each appear exactly once in every row and every column — the same rule Sudoku's rows and columns follow, just without the boxes.
  2. 2This row already shows a 2, a 4 and a 1. Only the 3 is unaccounted for.
  3. 3One candidate left in the cell makes it a Naked Single. Place the 3 — no clue needed at all.
2 4 1
  • Relationship — The arrow shows which cells support the deduction.
  • Conclusion — The final arrow lands beside the proved or ruled-out height.
Next in the ladder Hidden Single →

A height has only one possible cell left in this row or column, even though that cell has other candidates too.