Also known as:
The jigsaw, or pieceword, is simply a crossword that has been divided into blocks. Since all the answers are supplied, albeit in 3x3 chunks, and out of order, only a proportion of the clues are given. In many cases all the Across clues will be provided, but the puzzle can often be solved with just the first few rows of clues, or no clues at all.
Jigsaw crosswords usually have biaxial symmetry (top mirrors bottom, and left mirrors right), but the puzzle can be made more demanding with a central symmetry grid (top left mirrors bottom right, top right mirrors bottom left).
As in skeleton crosswords, no letter counts are given, as this would reveal too much information about the grid, so hyphenated words and phrases are usually avoided. Because many of the entries in the grid have no clues, proper nouns are also excluded. The solver needs to have some idea of the type of words that will appear in the finished puzzle, and allowing proper nouns would offer too much scope.
The more interlocking the grid, the easier it is for the solver, but the length of words in the grid also has a bearing on the puzzle's difficulty. Short words yield little information about surrounding blocks, but a long word will unlock a whole section of the grid.