Punctuating: put a space around every finished block
A finished block is a full stop. Cross out the squares on both sides, and the lines that cross those squares learn something new.
When is a block finished?
A run of boxes is finished when it cannot grow. The plainest case is a run as long as the biggest number in the clue. If a line says 3 2 and you have three boxes in a row, those three can never become four, so the squares just before and just after are empty.
A second case is a run at the edge. A box on the first square of a line belongs to the first clue, so once that run reaches the first number it is complete and the next square is empty. The mirror image holds at the right or bottom edge.
Practice: a 7x7 grid that needs punctuating
In this grid the empty squares around finished blocks are the only way into several lines.
Swipe the board sideways to see every column.
How we checked this grid: our solver knows nine named rules. With all of them it solves the grid in 22 line moves. With punctuating switched off it stops with 31 of 49 squares known. The first move that uses punctuating comes at step 5.
Your marks are saved in this browser, so you can come back to the grid.
What the crosses buy you
The cross is not decoration. Each one sits at the crossing of a row and a column, and in that other line it may close off a run, shorten the open stretch, or split a gap. Punctuate as soon as a block is finished and the other line gets the news straight away.
Skipping this step is the most common reason a puzzle seems stuck. The logic was there, but the squares that carried it were never marked.
The move in three steps
- Spot a finished block. Find a run as long as the biggest clue, or a run at an edge that has reached the first or last number.
- Cross both sides. Mark the square before and the square after as empty.
- Read the crossing lines. Check the row or column through each new cross.
Worked example: a column of twelve
A column of twelve has the clue 4 1 2. You have found a run of four boxes on squares 3 to 6. Four is the largest number in the clue, so the run cannot grow, and squares 2 and 7 get crosses.
At an edge it is even quicker. If squares 1 and 2 are boxes and the first number is 2, the first run is finished, and square 3 gets a cross at once.
Common slip. Crossing beside a run that still might grow. If a bigger clue is still unplaced, the run is not finished.
Punctuating, as Wikipedia describes it
Each link opens the source at the exact sentence.
- To solve the puzzle, it is usually also very important to enclose each bound or completed block of boxes immediately by separating spaces as described in Simple spaces method. sourceWikipedia: Nonogram
- Precise punctuating usually leads to more Forcing and may be vital for finishing the puzzle. sourceWikipedia: Nonogram
- First, the clue 1 is complete and there will be a space at each side of the bound block. sourceWikipedia: Nonogram
Sources: Wikipedia, Nonogram (revision 1377687149, read 2026-11-01). Wikipedia text available under CC BY-SA 4.0, edited by Wikipedia contributors. The source link after each sentence goes to the passage it comes from.
Keep going
GRIDS: daily nonogram
GRIDS gives you one picture a day. Try the technique on today's puzzle.
Play GRIDSQuestions
Is punctuating the same as simple spaces?
Close cousins. Wikipedia describes punctuating as the habit of enclosing blocks with spaces as in the simple spaces method. We keep them apart: punctuating crosses beside finished blocks, simple spaces crosses squares no block can reach.
Do I have to mark crosses?
The rules do not require it, but the marks are what lets the other lines use the fact. Use them.