Lesson 3 of 5
Solving techniques
4 min

Nonogram Edge Technique: Start From the Wall

The overlap works on empty lines. Once a line has a filled cell against one of its ends, the edge of the grid can do much more. This lesson carries on with the sailboat, with the overlaps from the last lesson done: rows 7 and 9, and all of row 10 and column 6.

Step 1 of 5

A block against the wall
Column 1's clue is 2, and its bottom cell, in row 10, is filled. A block can't run off the grid, so that filled cell is the end of the 2, and the block runs up from it: rows 9 and 10. Row 9 is filled, and row 8, just past the block, is empty.
Push off the wall
The wall decides where the block sits, so it decides the cell past it too.
Your move
Fill the rest of column 1's 2, and cross out the cell above it.
The same wall, twice more
The bottom edge works for every column with a filled bottom cell. Column 2's clue ends in 2, so its last block runs up from row 10 into row 9. Column 4's clue ends in 1, and a block of 1 is complete as soon as it is filled: the cell above it is empty.
Your move
Finish the bottom of columns 2 and 4: fill one starred cell and cross out the other two.
A cross is a wall too
Column 3's clue is 1 3. Its bottom cell is crossed out, and the cell above it, in row 9, is filled. A cross stops a block just as the edge does, so that filled cell ends a block. It can't be the 1, because the 3 comes after the 1 and there is no room left below. So the 3 ends in row 9: it is rows 7 to 9, and row 6 above it is empty.
Your move
Fill the rest of column 3's 3, and cross out the cell above it.
Your turn to read it
Column 5's clue is 3 4, and its bottom cell is filled. What does the bottom edge prove about column 5?
Question

What you learned

A filled cell against the edge of the grid is the end of a block: the block runs from it for its full length, and the cell after it is empty.
The same works from any of the four edges, for the first or the last block of a line.
A crossed-out cell is a wall as well.