GridWits
Medium tier Technique 10 of 31 Used by Smart Hint

Premature Loop

If an edge would close a smaller loop while lines or clues remain outside it, that edge is an X.

How it works

  1. 1Three sides of the centre cell are drawn and their ends are boxed in, so those three form one run of line whose two ends face each other across the cell's bottom edge.
  2. 2Drawing that bottom edge would close the run into a complete little loop right there, with nothing left to attach to.
  3. 3But there is already a separate line along the bottom of the board, and the finished puzzle is ONE loop — a closed square up here would strand that line outside it.
  4. 4So the bottom edge is ruled out: cross it off. (The rule has a mirror image worth remembering — if closing the loop really would account for every line on the board, that same edge becomes forced instead, and that is how a puzzle's very last edge gets drawn.)
  • Edge on the loop
  • Edge ruled out
  • Cells that establish the pattern
Next in the ladder Final Closure →

When closing the path here satisfies every clue and accounts for the whole loop, the closing edge is a line.