Step 4 of 5
One clue per patch
Every patch holds exactly one clue — which makes other clues into fences.
The rule of thumb: A patch can never swallow a second clue, so neighboring clues fence each other in.
It sounds too simple to be a technique, but it does more of the work than it looks. A clue’s patch must stop before it reaches the next clue, so when you list the ways a clue could go, every rectangle that would contain a second clue is out — however well it fits the badge and the number.
These practice boards each open with a clue that looks spoiled for choice: three or more rectangles fit its badge and number, until you throw out the ones that would swallow a neighboring clue. Then one fit remains. On busy boards, late in a solve, this fence is often the only reasoning you need.
Where to look: Clues with neighbors close by. For each shape the clue allows, ask not just “does it fit?” but “whose clue would it eat?”
Worked example
A real position from a board built around One clue per patch. Purple: what the reasoning rests on. Dashed: the patch in question. Green: what it proves.
Fences up. Last one: the check that chooses between two placements that both look fine. Step 5: Mind the leftovers →