A few weeks ago, we explained  what we see as the main reason for the abundance of black squares in cryptic crosswords: it forces you to solve every clue. Puzzle constructor extraordinaire Trip Payne  adds:
“There’s a second reason that is just as important, in my opinion: a standard crossword grid is forced to consist largely of very short words (5 letters and less), many of which appear constantly due to friendly letter patterns. In a typical cryptic grid, without the constraints of 100% checked letters, you can use longer words, and ones that haven’t been used very often before, without having to try to think of the millionth clue for AREA or ALOE.”
True enough: As we approach our first anniversary on this job, we have only had to reuse and re-clue words a handful of times. Still, the format we work in has a number of constraints.
Symmetry: Maintaining symmetry helps guarantee that the interesting words are spread around the diagram. In French crosswords, where there is no expectation of symmetry, the best entries are at and near 1 Across and 1 Down (the so-called gallows), and the most boring ones are in the opposite corner.
A related constraint is that when appropriate and possible, we try to place thematic entries in a symmetrical arrangement.
Grid geometry: A letter is “checked” if it appears in two words, across and down. We rigorously alternate checked and unchecked letters, avoiding consecutive checked letters and consecutive unchecked letters. Moreover, every row and column consists of precisely fifteen squares. So, for example, if we want to include a twelve-letter word, that forces three black squares in that row or column. The combination of these geometric concerns does restrict our options!
Three-letter words: In general we try to avoid three-letter words. But there are times when we have no alternative but to include them—for example, as a consequence of including many or long thematic words. When that happens, we try to have the three-letter words themselves be thematic (e.g. OIL in #3201, ONO in #3210.) If that isn’t possible, we might include them as part of a longer phrase (e.g., TEA FOR TWO AND TWO FOR TEA) that extends to other parts of the diagram, or as part of a longer word (e.g., the entry OFFEND appearing—and clued as—the charade OFF + END).
A side effect of avoiding three-letter words is that it becomes tricky to place eleven-letter words in the diagram, since the most convenient arrangement would be to combine an eleven-letter word with a black square and a three-letter word.
As for long entries—thirteen letters or longer, say—they bring their own issues into the construction process, but those are mostly about cluing. We’ll discuss those in a future post.