2. What's in a Crossword?

So, you're building a crossword. 

Much like in architecture, we need to put down our foundations first: figuring out our theme (if we're doing one), and then placing the black squares around that.

For this guide, we'll be building one of the Centre's Wordsearch grids: one where the crossword, once complete, becomes a wordsearch for a major Canadian city. This means that we are generally free to use whatever grid arrangement strikes our fancy - while following the rules of thumb laid out below.

Grid with diagonal symmetry.

Grid with horizontal symmetry.

Grid with no symmetry.

One of the most obvious characteristics of a crossword has to do with the way in which you've arranged your black squares ('blocks') across your canvas. Before talking about why you'd pick any one of the different arrangements shown above, though, I want to highlight what is the same across them all - those industry norms that, even if you're only looking to publish for fun, many solvers have come to expect.

• Every word is at least three letters long.
• Crosswords will trend to having more short words than long words. And with so many people making crosswords, that means that short words show up so much more often than longer words do. 
• Take the word GAS: according to this crossword-monitoring website, between the beginning of 2020 and the end of 2024, it was used 362 times. GASP, on the other hand - one letter longer - was used 156 times over the same time period. 
• That means that, to avoid having to come up with (and pretend to enjoy solving) thousands of clues for the words AT, IT, and UP, constructors and editors have made strenuous efforts to avoid using two-letter words.  
• Every white square is connected both horizontally and vertically to other white squares. 
• This is a (North) American crossword custom - British-style crosswords, known as 'cryptics', do not have the same rule.
• Having each white square crossed horizontally and vertically makes things easier for the solver. If they have no idea what the Across clue is, they have all of the intersecting Down clues to work with; and every time they figure out one of those answers, they get a letter to help them identify the Across answer.
• This built-in support system also means that you, as the crossword constructor, can have a little more flexibility in building your clues. You can push the envelope with that wordplay, or include a reference to a cultural niche that not everybody will know, because solvers can get help with that answer from the crossing clues (which means you may want to make those easier).

Grid without interconnectivity.

While keeping those minds, then, there are three main ways in which we can place our blocks. This question of symmetry (or asymmetry) is a much softer rule than the other two. While it has a certain aesthetic bonus to it, there's no gameplay-enhancing reason to obsess over it, like there is with the first two points.

• Diagonal symmetry means that the bottom-left corner will match the top-right, and the top-left corner will match the bottom-right. This is the most common type of symmetry, and may well be the default on your constructing software.
• If you are putting together a traditionally themed puzzle and your theme entries are paired off in terms of length, this is a great set-up. Place your themers in the mirrored entries created by the symmetry, and off you go!
• There is one exception to this need for pairing off: this diagonal symmetry has a blind spot, where the middle row/column is its own mirror. This means that a theme entry can be balanced in the middle.
• This is the most common set-up for publishers, and generally offers more flexibility to the constructor - with the important caveat of needing to pair off all themers (except one, which can be centred).
• Horizontal symmetry means that the leftmost column will match the rightmost column, while vertical symmetry means that the top row will match bottom row. 
• If you are putting together a themed puzzle and each of your theme entries can be centred in your grid, this can be a great set-up. Space out your themers, and off you go!
• To be more scientific about it: all of your themers need to be of a length where they can be centred in your grid. 
• If you are placing them horizontally in a grid with an odd number of columns, then all of the themers need to have an odd number of characters.
• If you are placing them vertically in a grid with an even number of columns, all of the themers need to have an even number of columns.
• You'll notice that there's a decent amount of empty space at the top and the bottom of this grid, and between each theme entry. That's because every word in the grid must be at least three letters - more on that below. That restriction can cramp the placement of your theme entries quite severely, and those restrictions will compound as you build the rest of your grid.
• Asymmetry means that there's no pattern dictating where the black squares will be placed. Follow your heart's desires, and let nobody stop you. (And off you go!)

Last things last: size doesn't matter. This is even less of a rule than symmetry, so it goes to the bottom of the page. 

Different publications will have different preferences - the Centre frequently publishes 11x11 (eleven rows, eleven columns) puzzles, while 15x15 is the size you'll see in most newspapers - but your only constraints here are the ones you put on yourself. You don't need to have the same number of rows and columns; and you are more than free to use blocks to make your puzzle look not like a rectangle, but like a heart, or a peace sign! 

The bigger your puzzle is, though, the harder it will be to fill out. And that - the actual strategy of how to use block placement - is what we'll discuss next.