We know that slot machines are made up of reels. But the collection of reels that make up a complete game has a variety of terms in the industry, including reel sets, boards and arrays.
The ability to determine the final outcome of the game comes when all the reels in an array come to a stop, and the pay lines (or ways) calculated based on what arrives. So the term reel set is important as that’s the confines in which a single game takes place. Each individual reel is important, but it’s the totality of all those reels coming to a stop that determines the final outcome on a traditional Vegas-style (Class III) slot machine.
Most slot machines historically have had one reel set, but nowadays with the popularity of games like Wonder 4 and Power 4, there’s a decent amount of slots with more than one array. Dancing Drums Power Trio is a recent example of a game with three reel sets.
At that point you’re playing multiple games concurrently, with each reel set being evaluated on its own for pays. You can get wins, or even bonuses, on multiple reel sets, but the rule of getting a certain number of bonus symbols within a single reel set traditionally is the norm.
Some exceptions, like the Reel Boost line of games on Light & Wonder, change it up by requiring bonus symbols to appear on at least 3 out of 4 reel sets instead.
Then there are games where the additional reel sets or boards come in the bonuses. Cheshire Cat, which we reviewed on the site recently, calls them arrays, and you can get up to four arrays with four wild reels per array in the free spins bonus.
But ultimately regardless of the term, the idea of a reel set, board or array is important to the overall design of a slot game, and that’s what it means when you see any of these terms on the slot!