As I mentioned in the Ingredient notes section, I like using thin-sliced rye bread for the canapés. The specific brand of rye bread I used here is called Mestemacher. It is a very thin, dense, and firm bread with hardly any crusts. This works well for canapés because although the bread is thin, it provides enough structure to hold the toppings well due to how firm and dense it is. And, because there are no crusts to cut off, you can use the entire piece of bread. If you can't find or don't like Mestemacher rye bread, you can use any type of rye bread. Or, substitute pumpernickel, or your favorite type of bread. If you are using a different type of bread and want it to be a little thinner, you can gently roll the bread with a rolling pin to flatten it some before cutting the slices into squares. But, try not to completely flatten the bread paper-thin; you still want it to have enough structure to hold up the toppings.